Ionizing radiation stable thermoplastic composition, method of making, and articles formed therefrom

ABSTRACT

A thermoplastic composition comprises a polycarbonate, and an aromatic sulfonate compound of formula
 
(Y) m —Ar—(Z—S(O) 2 —X) n  
 
wherein each X is independently a substituted or unsubstituted C 1 -C 20  alkyl, substituted or unsubstituted C 1 -C 20  arylalkyl, substituted or unsubstituted C 6 -C 20  aryl, or substituted or unsubstituted C 7 -C 40  alkylaryl; Z is —O—, or substituted or unsubstituted —(O—C 1-20 —) w —O—, wherein w is 1 to 20; Ar is a C 6 -C 62  aromatic group; m is 0-3 and n is 3-6; and each Y is independently C 1 -C 20  alkyl, substituted C 1 -C 20  alkyl, C 6 -C 20  aryl, C 1 -C 8  alkyl-substituted C 6 -C 20  aryl, halogen, nitro, C 1 -C 20  alkoxycarbonyl, C 1 -C 20  alkoxy, or C 1 -C 20  acyl, and further wherein a molded article having a thickness of 3.2±0.12 millimeters and consisting of the polycarbonate, aromatic sulfonate compound, and an effective amount of each of a mold-release agent and an antioxidant has, after exposure to a total gamma radiation dose of 83 kGy and when measured according to ASTM D1925-70, an increase in yellowness index (dYI) of less than or equal to 45, when compared to the unexposed molded article. Methods of making the thermoplastic composition, and articles prepared therefrom, are also disclosed.

BACKGROUND OF THE INVENTION

This disclosure relates to stabilized thermoplastic compositions,methods of manufacture, and articles and uses thereof.

Irradiation using electron beam (e-beam) radiation or gamma ray (γ-ray)radiation (also referred to as “gamma radiation”) is increasingly usedto sterilize lightweight or disposable plastic articles for use inhospitals, biological laboratories, manufacturers of medical devices,and other end-users of sterile equipment. Gamma ray sources such as, forexample, ⁶⁰Co, which emits a β-particle and gamma ray radiation at 1.17and 1.33 megaelectron volts (MeV), can be used for sterilization. Someadvantages of gamma ray radiation are that it is more penetrating thanE-beam radiation, leaves no residue, and can be less damaging toplastics than heat and/or moisture. Because of the ability of gamma raysto penetrate plastics, articles that have already been packaged and/orassembled may conveniently be sterilized. Further, use of such radiationis ideal for sterilizing large numbers of articles, such as those madefrom plastics, due to the penetrating ability of gamma radiation,wherein the units closer to the source can receive a similar dose tothose furthest from the source. Articles such as blood bags, petridishes, syringes, beakers, vials, centrifuge tubes, spatulas, and thelike, as well as prepackaged articles, are desirably sterilized usingthis method.

Thermoplastics are useful for preparing articles such as those listedabove. In particular, polycarbonates, with their balance of propertiesincluding transparency, low color, impact resistance, ductility, andmelt flow, are desirable for use as materials of construction. However,exposure of polycarbonates to gamma ray doses suitable for sterilization(typically nominal doses of 10 to 85 kiloGrays (kGy), where 1 Grayequals 1 Joule of absorbed energy per kilogram of mass) can result inobservable yellowing of the polycarbonate, and may further result in thedegradation of one or more mechanical properties. Colorants may be addedin order to offset the yellowness resulting from sterilization ofpolycarbonate compositions. However, because the amount of colorantadded to the polycarbonate is often selected for a given radiation dose,exposure dose variations due to process variability or re-sterilizationcan create color differences that may be noticeable to the eye.

Stabilizers, also referred to in the art as “antirads”, may be used tomitigate the effects of the gamma ray dose on plastics generally.Stabilizers present in amounts sufficient to reduce yellowing inthermoplastic compositions comprising polycarbonates may also affect oneor more of the desirable mechanical properties of the thermoplasticcomposition, such as, for example, impact strength and/or ductility. Theusefulness of stabilizers to reduce yellowing in thermoplasticcompositions of polycarbonate upon gamma ray exposure can, in this way,be mitigated by these secondary considerations of mechanical properties.

There accordingly remains a need in the art for improved stabilizers forpolycarbonate compositions, as well as polycarbonate compositions havingimproved resistance to gamma ray radiation.

SUMMARY OF THE INVENTION

The above deficiencies in the art are alleviated by, in an embodiment, athermoplastic composition comprising a polycarbonate, and an aromaticsulfonate compound of formula:(Y)_(m)—Ar—(Z—S(O)₂—X)_(n)wherein each X is independently a substituted or unsubstituted C₁-C₂₀alkyl, substituted or unsubstituted C₁-C₂₀ arylalkyl, substituted orunsubstituted C₆-C₂₀ aryl, or substituted or unsubstituted C₇-C₄₀alkylaryl; Z is —O—, or substituted or unsubstituted —(O—C₁₋₂₀—)_(w)—O—,wherein w is 1 to 20; Ar is a C₆-C₆₂ aromatic group; m is 0-3 and n is3-6; and each Y is independently C₁-C₂₀ alkyl, substituted C₁-C₂₀ alkyl,C₆-C₂₀ aryl, C₁-C₈ alkyl-substituted C₆-C₂₀ aryl, halogen, nitro, C₁-C₂₀alkoxycarbonyl, C₁-C₂₀ alkoxy, or C₁-C₂₀ acyl, and further wherein amolded article having a thickness of 3.2±0.12 millimeters and consistingof the polycarbonate, aromatic sulfonate compound, and an effectiveamount of each of a mold-release agent and an antioxidant has, afterexposure to a total gamma radiation dose of 83 kGy and when measuredaccording to ASTM D1925-70, an increase in yellowness index (dYI) ofless than or equal to 45, when compared to the unexposed molded article.

In another embodiment, a thermoplastic composition comprises apolycarbonate, and 0.001 to 500 millimoles per kilogram (mmol/Kg) of anaromatic sulfonate compound of formula(Y)_(m)—Ar—(Z—S(O)₂—X)_(n)wherein each X is independently a substituted or unsubstituted C₁-C₂₀alkyl, substituted or unsubstituted C₁-C₂₀ arylalkyl, substituted orunsubstituted C₆-C₂₀ aryl, or substituted or unsubstituted C₇-C₄₀alkylaryl; Z is —O—, or substituted or unsubstituted —(O—C₁₋₂₀—)_(w)—O—,wherein w is 1 to 20; Ar is a C₆-C₆₂ aromatic group; m is 0-3 and n is3-6; and each Y is independently C₁-C₂₀ alkyl, substituted C₁-C₂₀ alkyl,C₆-C₂₀ aryl, C₁-C₈ alkyl-substituted C₆-C₂₀ aryl, halogen, nitro, C₁-C₂₀alkoxycarbonyl, C₁-C₂₀ alkoxy, or C₁-C₂₀ acyl, wherein the amount ofaromatic sulfonate compound is based on the total weight of thepolycarbonate and aromatic sulfonate compound.

In another embodiment, a method of forming a thermoplastic compositioncomprises melt blending a polycarbonate and an aromatic sulfonatecompound of formula:(Y)_(m)—Ar—(Z—S(O)₂—X)_(n)wherein each X is independently a substituted or unsubstituted C₁-C₂₀alkyl, substituted or unsubstituted C₁-C₂₀ arylalkyl, substituted orunsubstituted C₆-C₂₀ aryl, or substituted or unsubstituted C₇-C₄₀alkylaryl; Z is —O—, or substituted or unsubstituted —(O—C₁₋₂₀—)_(w)—O—,wherein w is 1 to 20; Ar is a C₆-C₆₂ aromatic group; m is 0-3 and n is3-6; and each Y is independently C₁-C₂₀ alkyl, substituted C₁-C₂₀ alkyl,C₆-C₂₀ aryl, C₁-C₈ alkyl-substituted C₆-C₂₀ aryl, halogen, nitro, C₁-C₂₀alkoxycarbonyl, C₁-C₂₀ alkoxy, or C₁-C₂₀ acyl, and further wherein amolded article having a thickness of 3.2±0.12 millimeters and consistingof the polycarbonate, aromatic sulfonate compound, and an effectiveamount of each of a mold-release agent and an antioxidant has, afterexposure to a total gamma radiation dose of 83 kGy and when measuredaccording to ASTM D1925-70, an increase in yellowness index (dYI) ofless than or equal to 45, when compared to the unexposed molded article.

In another embodiment, a masterbatch composition comprises apolycarbonate, and 5 to 500 mmol/Kg of an aromatic sulfonate compound offormula:(Y)_(m)—Ar—(Z—S(O)₂—X)_(n)wherein each X is independently a substituted or unsubstituted C₁-C₂₀alkyl, substituted or unsubstituted C₁-C₂₀ arylalkyl, substituted orunsubstituted C₆-C₂₀ aryl, or substituted or unsubstituted C₇-C₄₀alkylaryl; Z is —O—, or substituted or unsubstituted —(O—C₁₋₂₀—)_(w)—O—,wherein w is 1 to 20; Ar is a C₆-C₆₂ aromatic group; m is 0-3 and n is3-6; and each Y is independently C₁-C₂₀ alkyl, substituted C₁-C₂₀ alkyl,C₆-C₂₀ aryl, C₁-C₈ alkyl-substituted C₆-C₂₀ aryl, halogen, nitro, C₁-C₂₀alkoxycarbonyl, C₁-C₂₀ alkoxy, or C₁-C₂₀ acyl, wherein the amount ofaromatic sulfonate compound is based on the total weight of thepolycarbonate and aromatic sulfonate compound, and wherein athermoplastic composition comprises a masterbatch composition and apolycarbonate resin.

In another embodiment, a method of making a thermoplastic compositioncomprises melt-blending: a masterbatch composition comprising apolycarbonate, and an aromatic sulfonate compound of formula:(Y)_(m)—Ar—(Z—S(O)₂—X)_(n)wherein each X is independently a substituted or unsubstituted C₁-C₂₀alkyl, substituted or unsubstituted C₁-C₂₀ arylalkyl, substituted orunsubstituted C₆-C₂₀ aryl, or substituted or unsubstituted C₇-C₄₀alkylaryl, Z is —O— or substituted or unsubstituted —(O—C₁₋₂₀—)_(w)—O—,wherein w is 1 to 20, Ar is a C₆-C₆₂ aromatic group, m is 0-3 and n is3-6, and each Y is independently C₁-C₂₀ alkyl, substituted C₁-C₂₀ alkyl,C₆-C₂₀ aryl, C₁-C₈ alkyl-substituted C₆-C₂₀ aryl, halogen, nitro, C₁-C₂₀alkoxycarbonyl, C₁-C₂₀ alkoxy, or C₁-C₂₀ acyl; and a polycarbonateresin, and wherein a molded article having a thickness of 3.2±0.12millimeters and consisting of the polycarbonate, aromatic sulfonatecompound, the polycarbonate resin, and an effective amount of each of amold-release agent and an antioxidant has, after exposure to a totalgamma radiation dose of 83 kGy and when measured according to ASTMD1925-70, an increase in yellowness index (dYI) of less than or equal to45, when compared to the unexposed molded article.

In another embodiment, an article comprising the thermoplasticcomposition is disclosed.

The above described and other features are exemplified by the followingdetailed description.

DETAILED DESCRIPTION OF THE INVENTION

Surprisingly, it has been found that a thermoplastic compositioncomprising a polycarbonate, a specific type of aromatic sulfonatecompound, and an optional ionizing radiation stabilizing additive hassignificantly improved resistance to yellowing upon exposure to gammaradiation. The aromatic sulfonate compound is advantageously present inan amount that is lower than an amount of other known stabilizers neededto afford a comparable resistance to yellowing after gamma radiationexposure in a comparable polycarbonate-containing composition. The useof the aromatic sulfonate compound helps maintain the mechanicalproperties at the same or comparable level as an unstabilizedthermoplastic composition comprising polycarbonate.

As used herein, the term “alkyl” refers to a straight or branched chainmonovalent hydrocarbon group; “alkylene” refers to a straight orbranched chain divalent hydrocarbon group; “alkylidene” refers to astraight or branched chain divalent hydrocarbon group, with bothvalences on a single common carbon atom; “alkenyl” refers to a straightor branched chain monovalent hydrocarbon group having at least twocarbons joined by a carbon-carbon double bond; “cycloalkyl” refers to anon-aromatic monovalent monocyclic or multicylic hydrocarbon grouphaving at least three carbon atoms, “cycloalkylene” refers to anon-aromatic alicyclic divalent hydrocarbon group having at least threecarbon atoms, with at least one degree of unsaturation; “aryl” refers toan aromatic monovalent group containing only carbon in the aromatic ringor rings; “arylene” refers to an aromatic divalent group containing onlycarbon in the aromatic ring or rings; “alkylaryl” refers to an arylgroup that has been substituted with an alkyl group as defined above,with 4-methylphenyl being an exemplary alkylaryl group; “arylalkyl”refers to an alkyl group that has been substituted with an aryl group asdefined above, with benzyl being an exemplary arylalkyl group; “acyl”refers to a an alkyl group as defined above with the indicated number ofcarbon atoms attached through a carbonyl carbon bridge (—C(═O)—);“alkoxy” refers to an alkyl group as defined above with the indicatednumber of carbon atoms attached through an oxygen bridge (—O—); and“aryloxy” refers to an aryl group as defined above with the indicatednumber of carbon atoms attached through an oxygen bridge (—O—).

Unless otherwise indicated, each of the foregoing groups may beunsubstituted or substituted, provided that the substitution does notsignificantly adversely affect synthesis, stability, or use of thecompound. The term “substituted” as used herein means that any one ormore hydrogens on the designated atom or group is replaced with anothergroup, provided that the designated atom's normal valence is notexceeded. When the substituent is oxo (i.e., ═O), then two hydrogens onthe atom are replaced. Combinations of substituents and/or variables arepermissible provided that the substitutions do not significantlyadversely affect synthesis or use of the compound.

Exemplary groups that may be present on a “substituted” positioninclude, but are not limited to, halogen; cyano; hydroxyl; nitro; azido;alkanoyl (such as a C₂-C₆ alkanoyl group such as acyl or the like);carboxamido; alkyl groups (typically having 1 to about 8 carbon atoms,or 1 to about 6 carbon atoms); cycloalkyl groups, alkenyl and alkynylgroups (including groups having one or more unsaturated linkages andfrom 2 to about 8, or 2 to about 6 carbon atoms); alkoxy groups havingone or more oxygen linkages and from 1 to about 8, or from 1 to about 6carbon atoms; aryloxy such as phenoxy; alkylthio groups including thosehaving one or more thioether linkages and from 1 to about 8 carbonatoms, or from 1 to about 6 carbon atoms; alkylsulfinyl groups includingthose having one or more sulfinyl linkages and from 1 to about 8 carbonatoms, or from 1 to about 6 carbon atoms; alkylsulfonyl groups includingthose having one or more sulfonyl linkages and from 1 to about 8 carbonatoms, or from 1 to about 6 carbon atoms; aminoalkyl groups includinggroups having one or more N atoms and from 1 to about 8, or from 1 toabout 6 carbon atoms; aryl having 6 or more carbons and one or morerings, (e.g., phenyl, biphenyl, naphthyl, or the like, each ring eithersubstituted or unsubstituted aromatic); arylalkyl having 1 to 3 separateor fused rings and from 6 to about 18 ring carbon atoms, with benzylbeing an exemplary arylalkyl group; or arylalkoxy having 1 to 3 separateor fused rings and from 6 to about 18 ring carbon atoms, with benzyloxybeing an exemplary arylalkoxy group.

The thermoplastic composition comprises a polycarbonate. As used herein,the terms “polycarbonate” and “polycarbonate resin” means compositionshaving repeating structural carbonate units of the formula (1):

in which at least 60 percent of the total number of R¹ groups arearomatic organic radicals and the balance thereof are aliphatic,alicyclic, or aromatic radicals. In one embodiment, each R¹ is anaromatic organic radical, for example a radical of the formula (2):-A¹-Y¹-A²-  (2)wherein each of A¹ and A² is a monocyclic divalent aryl radical and Y¹is a bridging radical having one or two atoms that separate A¹ from A².In an exemplary embodiment, one atom separates A¹ from A². Illustrativenon-limiting examples of radicals of this type are —O—, —S—, —S(O)—,—S(O₂)—, —C(O)—, methylene, cyclohexyl-methylene,2-[2.2.1]-bicycloheptylidene, ethylidene, isopropylidene,neopentylidene, cyclohexylidene, cyclopentadecylidene,cyclododecylidene, and adamantylidene. The bridging radical Y¹ may be ahydrocarbon group or a saturated hydrocarbon group such as methylene,cyclohexylidene, or isopropylidene.

Polycarbonates may be produced by the interfacial reaction of dihydroxycompounds having the formula HO—R¹—OH, which includes dihydroxycompounds of formula (3)HO-A¹-Y¹-A²-OH  (3)wherein Y¹, A¹ and A² are as described above. Also included arebisphenol compounds of general formula (4):

wherein R^(a) and R^(b) each represent a halogen atom or a monovalenthydrocarbon group and may be the same or different; p and q are eachindependently integers of 0 to 4; and X^(a) represents one of the groupsof formula (5):

wherein R^(c) and R^(d) each independently represent a hydrogen atom ora monovalent linear or cyclic hydrocarbon group and R^(e) is a divalenthydrocarbon group.

Some illustrative, non-limiting examples of suitable dihydroxy compoundsinclude the following: resorcinol, 4-bromoresorcinol, hydroquinone,4,4′-dihydroxybiphenyl, 1,6-dihydroxynaphthalene,2,6-dihydroxynaphthalene, bis(4-hydroxyphenyl)methane,bis(4-hydroxyphenyl)diphenylmethane,bis(4-hydroxyphenyl)-1-naphthylmethane, 1,2-bis(4-hydroxyphenyl)ethane,1,1-bis(4-hydroxyphenyl)-1-phenylethane,2-(4-hydroxyphenyl)-2-(3-hydroxyphenyl)propane,bis(4-hydroxyphenyl)phenylmethane,2,2-bis(4-hydroxy-3-bromophenyl)propane,1,1-bis(hydroxyphenyl)cyclopentane, 1,1-bis(4-hydroxyphenyl)cyclohexane,1,1-bis(4-hydroxy-3methyl phenyl)cyclohexane1,1-bis(4-hydroxyphenyl)isobutene,1,1-bis(4-hydroxyphenyl)cyclododecane,trans-2,3-bis(4-hydroxyphenyl)-2-butene,2,2-bis(4-hydroxyphenyl)adamantine, (alpha,alpha′-bis(4-hydroxyphenyl)toluene, bis(4-hydroxyphenyl)acetonitrile,2,2-bis(3-methyl-4-hydroxyphenyl)propane,2,2-bis(3-ethyl-4-hydroxyphenyl)propane,2,2-bis(3-n-propyl-4-hydroxyphenyl)propane,2,2-bis(3-isopropyl-4-hydroxyphenyl)propane,2,2-bis(3-sec-butyl-4-hydroxyphenyl)propane,2,2-bis(3-t-butyl-4-hydroxyphenyl)propane,2,2-bis(3-cyclohexyl-4-hydroxyphenyl)propane,2,2-bis(3-allyl-4-hydroxyphenyl)propane,2,2-bis(3-methoxy-4-hydroxyphenyl)propane,2,2-bis(4-hydroxyphenyl)hexafluoropropane,1,1-dichloro-2,2-bis(4-hydroxyphenyl)ethylene,1,1-dibromo-2,2-bis(4-hydroxyphenyl)ethylene,1,1-dichloro-2,2-bis(5-phenoxy-4-hydroxyphenyl)ethylene,4,4′-dihydroxybenzophenone, 3,3-bis(4-hydroxyphenyl)-2-butanone,1,6-bis(4-hydroxyphenyl)-1,6-hexanedione, ethylene glycolbis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl)ether,bis(4-hydroxyphenyl)sulfide, bis(4-hydroxyphenyl)sulfoxide,bis(4-hydroxyphenyl)sulfone, 9,9-bis(4-hydroxyphenyl)fluorine,2,7-dihydroxypyrene, 6,6′-dihydroxy-3,3,3′,3′-tetramethylspiro(bis)indane(“spirobiindane bisphenol”),3,3-bis(4-hydroxyphenyl)phthalide, 2,6-dihydroxydibenzo-p-dioxin,2,6-dihydroxythianthrene, 2,7-dihydroxyphenoxathin,2,7-dihydroxy-9,10-dimethylphenazine, 3,6-dihydroxydibenzofuran,3,6-dihydroxydibenzothiophene, and 2,7-dihydroxycarbazole, and the like,as well as combinations comprising at least one of the foregoingdihydroxy compounds.

Specific examples of the types of bisphenol compounds represented byformula (3) include 1,1-bis(4-hydroxyphenyl)methane,1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane(hereinafter “bisphenol A” or “BPA”), 2,2-bis(4-hydroxyphenyl)butane,2,2-bis(4-hydroxyphenyl)octane, 1,1-bis(4-hydroxyphenyl)propane,1,1-bis(4-hydroxyphenyl)n-butane,2,2-bis(4-hydroxy-1-methylphenyl)propane,1,1-bis(4-hydroxy-t-butylphenyl)propane,3,3-bis(4-hydroxyphenyl)phthalimidine,2-phenyl-3,3-bis(4-hydroxyphenyl)phthalimidine (PPPBP), and1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane (DMBPC). Combinationscomprising at least one of the foregoing dihydroxy compounds may also beused.

Branched polycarbonates are also useful, as well as blends of a linearpolycarbonate and a branched polycarbonate. The branched polycarbonatesmay be prepared by adding a branching agent during polymerization. Thesebranching agents include polyfunctional organic compounds containing atleast three functional groups selected from hydroxyl, carboxyl,carboxylic anhydride, haloformyl, and mixtures of the foregoingfunctional groups. Specific examples include trimellitic acid,trimellitic anhydride, trimellitic trichloride, tris-p-hydroxy phenylethane, isatin-bis-phenol, tris-phenol TC(1,3,5-tris((p-hydroxyphenyl)isopropyl)benzene), tris-phenol PA(4(4(1,1-bis(p-hydroxyphenyl)-ethyl)alpha, alpha-dimethylbenzyl)phenol), 4-chloroformyl phthalic anhydride, trimesic acid, andbenzophenone tetracarboxylic acid. The branching agents may be added ata level of 0.05 to 2.0 wt % of the polycarbonate. All types ofpolycarbonate end groups are contemplated as being useful in thepolycarbonate, provided that such end groups do not significantly affectdesired properties of the thermoplastic compositions.

In a specific embodiment, the polycarbonate is a linear homopolymerderived from bisphenol A, in which each of A¹ and A² is p-phenylene andY¹ is isopropylidene. The polycarbonates may have an intrinsicviscosity, as determined in chloroform at 25° C., of 0.3 to 1.5deciliters per gram (dl/g), specifically 0.45 to 1.0 dl/g. Thepolycarbonates may have a weight average molecular weight (Mw) of 10,000to 100,000, as measured by gel permeation chromatography (GPC) using acrosslinked styrene-divinyl benzene column, at a sample concentration of1 milligram per milliliter, and as calibrated with polycarbonatestandards.

In an embodiment, the polycarbonate has flow properties suitable for themanufacture of thin articles. Melt volume flow rate (often abbreviatedMVR) measures the rate of extrusion of a thermoplastics through anorifice at a prescribed temperature and load. Polycarbonates suitablefor the formation of thin articles may have an MVR, measured at 300°C./1.2 kg according to ASTM D1238-04, of 0.5 to 80 cubic centimeters per10 minutes (cc/10 min). In a specific embodiment, a suitablepolycarbonate composition has an MVR measured at 300° C./1.2 kgaccording to ASTM D1238-04, of 0.5 to 50 cc/10 min, specifically 0.5 to25 cc/10 min, and more specifically 1 to 15 cc/10 min. Mixtures ofpolycarbonates of different flow properties may be used to achieve theoverall desired flow property.

The polycarbonate may have a light transmittance greater than or equalto 55%, specifically greater than or equal to 60% and more specificallygreater than or equal to 70%, as measured at 3.2±0.12 millimetersthickness according to ASTM D1003-00. The polycarbonate may also have ahaze less than or equal to 50%, specifically less than or equal to 40%,and most specifically less than or equal to 30%, as measured at 3.2±0.12millimeters thickness according to ASTM DI 003-00.

“Polycarbonates” and “polycarbonate resin” as used also refers tocopolymers comprising carbonate chain units. A specific suitablecopolymer is a polyester-polycarbonate, also known as acopolyester-polycarbonate and polyester-carbonate. Combinations ofpolycarbonates and polyester-polycarbonates may also be used. As usedherein, a “combination” is inclusive of all mixtures, blends, alloys,reaction products, and the like. Polyester-polycarbonates contain, inaddition to recurring carbonate chain units of the formula (1),repeating units of formula (6):

wherein D is a divalent radical derived from a dihydroxy compound, andmay be, for example, a C₂₋₁₀ alkylene radical, a C₆₋₂₀ alicyclicradical, a C₆₋₂₀ aromatic radical or a polyoxyalkylene radical in whichthe alkylene groups contain 2 to 6 carbon atoms, specifically 2, 3, or 4carbon atoms; and T divalent radical derived from a dicarboxylic acid,and may be, for example, a C₂₋₁₀ alkylene radical, a C₆₋₂₀ alicyclicradical, a C₆₋₂₀ alkyl aromatic radical, or a C₆₋₂₀ aromatic radical.

In one embodiment, D is a C₂₋₆ alkylene radical. In another embodiment,D is derived from an aromatic dihydroxy compound of formula (7):

wherein each R^(f) is independently a halogen atom, a C₁₋₁₀ hydrocarbongroup, or a C₁₋₁₀ halogen substituted hydrocarbon group, and n is 0 to4. The halogen is usually bromine. Examples of compounds that may berepresented by the formula (7) include resorcinol, substitutedresorcinol compounds such as 5-methyl resorcinol, 5-ethyl resorcinol,5-propyl resorcinol, 5-butyl resorcinol, 5-t-butyl resorcinol, 5-phenylresorcinol, 5-cumyl resorcinol, 2,4,5,6-tetrafluoro resorcinol,2,4,5,6-tetrabromo resorcinol, or the like; catechol; hydroquinone;substituted hydroquinones such as 2-methyl hydroquinone, 2-ethylhydroquinone, 2-propyl hydroquinone, 2-butyl hydroquinone, 2-t-butylhydroquinone, 2-phenyl hydroquinone, 2-cumyl hydroquinone,2,3,5,6-tetramethyl hydroquinone, 2,3,5,6-tetra-t-butyl hydroquinone,2,3,5,6-tetrafluoro hydroquinone, 2,3,5,6-tetrabromo hydroquinone, orthe like; or combinations comprising at least one of the foregoingcompounds.

Examples of aromatic dicarboxylic acids that may be used to prepare thepolyesters include isophthalic or terephthalic acid,1,2-di(p-carboxyphenyl)ethane, 4,4′-dicarboxydiphenyl ether,4,4′-bisbenzoic acid, and mixtures comprising at least one of theforegoing acids. Acids containing fused rings can also be present, suchas in 1,4-, 1,5-, or 2,6-naphthalenedicarboxylic acids. Specificdicarboxylic acids are terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexane dicarboxylic acid, or mixtures thereof. Aspecific dicarboxylic acid comprises a mixture of isophthalic acid andterephthalic acid wherein the weight ratio of terephthalic acid toisophthalic acid is 91:1 to 2:98. In another specific embodiment, D is aC₂₋₆ alkylene radical and T is p-phenylene, m-phenylene, naphthalene, adivalent cycloaliphatic radical, or a mixture thereof. This class ofpolyester includes the poly(alkylene terephthalates).

In addition to the ester units, the polyester-polycarbonates comprisecarbonate units as described hereinabove. Carbonate units of formula (1)may also be derived from aromatic dihydroxy compounds of formula (7),wherein specific carbonate units are resorcinol carbonate units.

Specifically, the polyester unit of a polyester-polycarbonate can bederived from the reaction of a combination of isophthalic andterephthalic diacids (or derivatives thereof) with resorcinol, bisphenolA, or a combination comprising at least one of these, wherein the molarratio of isophthalate units to terephthalate units is 91:9 to 2:98,specifically 85:15 to 3:97, more specifically 80:20 to 5:95, and stillmore specifically 70:30 to 10:90. The polycarbonate units can be derivedfrom resorcinol and/or bisphenol A, in a molar ratio of resorcinolcarbonate units to bisphenol A carbonate units of 0:100 to 99:1, and themolar ratio of the mixed isophthalate-terephthalate polyester units tothe polycarbonate units in the polyester-polycarbonate can be 1:99 to99:1, specifically 5:95 to 90:10, more specifically 10:90 to 80:20.Where a blend of polyester-polycarbonate with polycarbonate is used, theratio of polycarbonate to polyester-polycarbonate in the blend can be,respectively, 1:99 to 99:1, specifically 10:90 to 90:10.

The polyester-polycarbonates may have a weight-averaged molecular weight(Mw) of 1,500 to 100,000, specifically 1,700 to 50,000, and morespecifically 2,000 to 40,000. Molecular weight determinations areperformed using gel permeation chromatography (GPC), using a crosslinkedstyrene-divinylbenzene column and calibrated to polycarbonatereferences. Samples are prepared at a concentration of about 1 mg/ml,and are eluted at a flow rate of about 1.0 ml/min.

Suitable polycarbonates can be manufactured by processes such asinterfacial polymerization and melt polymerization. Although thereaction conditions for interfacial polymerization may vary, anexemplary process generally involves dissolving or dispersing a dihydricphenol reactant in aqueous caustic soda or potash, adding the resultingmixture to a suitable water-immiscible solvent medium, and contactingthe reactants with a carbonate precursor in the presence of a suitablecatalyst such as triethylamine or a phase transfer catalyst, undercontrolled pH conditions, e.g., 8 to 10. The most commonly used waterimmiscible solvents include methylene chloride, 1,2-dichloroethane,chlorobenzene, toluene, and the like. Suitable carbonate precursorsinclude, for example, a carbonyl halide such as carbonyl bromide orcarbonyl chloride, or a haloformate such as a bishaloformates of adihydric phenol (e.g., the bischloroformates of bisphenol A,hydroquinone, or the like) or a glycol (e.g., the bishaloformate ofethylene glycol, neopentyl glycol, polyethylene glycol, or the like).Combinations comprising at least one of the foregoing types of carbonateprecursors may also be used. A chain stopper (also referred to as acapping agent) may be included during polymerization. The chain-stopperlimits molecular weight growth rate, and so controls molecular weight inthe polycarbonate. A chain-stopper may be at least one of mono-phenoliccompounds, mono-carboxylic acid chlorides, and/or mono-chloroformates.

For example, mono-phenolic compounds suitable as chain stoppers includemonocyclic phenols, such as phenol, C₁-C₂₂ alkyl-substituted phenols,p-cumyl-phenol, p-tertiary-butyl phenol, hydroxy diphenyl; monoethers ofdiphenols, such as p-methoxyphenol. Alkyl-substituted phenols includethose with branched chain alkyl substituents having 8 to 9 carbon atoms.A mono-phenolic UV absorber may be used as capping agent. Such compoundsinclude 4-substituted-2-hydroxybenzophenones and their derivatives, arylsalicylates, monoesters of diphenols such as resorcinol monobenzoate,2-(2-hydroxyaryl)-benzotriazoles and their derivatives,2-(2-hydroxyaryl)-1,3,5-triazines and their derivatives, and the like.Specifically, mono-phenolic chain-stoppers include phenol,p-cumylphenol, and/or resorcinol monobenzoate.

Mono-carboxylic acid chlorides may also be suitable as chain stoppers.These include monocyclic, mono-carboxylic acid chlorides such as benzoylchloride, C₁-C₂₂ alkyl-substituted benzoyl chloride, toluoyl chloride,halogen-substituted benzoyl chloride, bromobenzoyl chloride, cinnamoylchloride, 4-nadimidobenzoyl chloride, and mixtures thereof; polycyclic,mono-carboxylic acid chlorides such as trimellitic anhydride chloride,and naphthoyl chloride; and mixtures of monocyclic and polycyclicmono-carboxylic acid chlorides. Chlorides of aliphatic monocarboxylicacids with up to 22 carbon atoms are suitable. Functionalized chloridesof aliphatic monocarboxylic acids, such as acryloyl chloride andmethacryoyl chloride, are also suitable. Also suitable aremono-chloroformates including monocyclic, mono-chloroformates, such asphenyl chloroformate, alkyl-substituted phenyl chloroformate, p-cumylphenyl chloroformate, toluene chloroformate, and mixtures thereof.

The polyester-polycarbonates may be prepared by interfacialpolymerization. Rather than utilizing the dicarboxylic acid per se, itis possible, and sometimes even preferred, to employ the reactivederivatives of the acid, such as the corresponding acid halides, inparticular the acid dichlorides and the acid dibromides. Thus, forexample instead of using isophthalic acid, terephthalic acid, ormixtures thereof, it is possible to employ isophthaloyl dichloride,terephthaloyl dichloride, and mixtures thereof.

Among the phase transfer catalysts that may be used are catalysts of theformula (R³)₄Q⁺X, wherein each R³ is the same or different, and is aC₁₋₁₀ alkyl group; Q is a nitrogen or phosphorus atom; and X is ahalogen atom or a C₁₋₈ alkoxy group or C₆₋₁₈ aryloxy group. Suitablephase transfer catalysts include, for example, [CH₃(CH₂)₃]₄NX,[CH₃(CH₂)₃]₄PX, [CH₃(CH₂)₅]₄NX, [CH₃(CH₂)₆]₄NX, [CH₃(CH₂)₄]₄NX,CH₃[CH₃(CH₂)₃]₃NX, and CH₃[CH₃(CH₂)₂]₃NX, wherein X is Cl^(−, Br)^(−, a C) ₁₋₈ alkoxy group or a C₆₋₁₈ aryloxy group. An effective amountof a phase transfer catalyst may be 0.1 to 10 wt % based on the weightof bisphenol in the phosgenation mixture. In another embodiment aneffective amount of phase transfer catalyst may be 0.5 to 2 wt % basedon the weight of bisphenol in the phosgenation mixture.

Alternatively, melt processes may be used to make the polycarbonates.Generally, in the melt polymerization process, polycarbonates may beprepared by co-reacting, in a molten state, the dihydroxy reactant(s)and a diaryl carbonate ester, such as diphenyl carbonate, in thepresence of a transesterification catalyst in a Banbury® mixer, twinscrew extruder, or the like to form a uniform dispersion. Volatilemonohydric phenol is removed from the molten reactants by distillationand the polymer is isolated as a molten residue. A specifically usefulmelt process for making polycarbonates uses a diaryl carbonate esterhaving electron withdrawing substituents on the aryls. Examples ofspecifically useful diaryl carbonate esters with electron withdrawingsubstituents include bis(4-nitrophenyl)carbonate,bis(2-chlorophenyl)carbonate, bis(4-chlorophenyl)carbonate, bis(methylsalicyl)carbonate, bis(4-methylcarboxylphenyl)carbonate,bis(2-acetylphenyl)carboxylate, bis(4-acetylphenyl) carboxylate, or acombination comprising at least one of these. In addition, suitabletransesterification catalyst for use may include phase transfercatalysts of formula (R³)₄Q⁺X above, wherein each R³, Q, and X are asdefined above. Examples of suitable transesterification catalystsinclude tetrabutylammonium hydroxide, tetrabutylammonium acetate,tetrabutylphosphonium hydroxide, tetrabutylphosphonium acetate,tetrabutylphosphonium phenolate, or a combination comprising at leastone of these.

In addition to the homopolycarbonates, polyester-polycarbonates, andcombinations of these as described above, it is also possible to usecombinations of the homopolycarbonates and polyester-polycarbonates withother thermoplastic polymers, for example combinations ofhomopolycarbonates and/or polycarbonate copolymers with polyesters.Suitable polyesters comprise repeating units of formula (6), and may be,for example, poly(alkylene dicarboxylates), liquid crystallinepolyesters, and polyester copolymers. It is also possible to use abranched polyester in which a branching agent, for example, a glycolhaving three or more hydroxyl groups or a trifunctional ormultifunctional carboxylic acid has been incorporated. Furthermore, itis sometime desirable to have various concentrations of acid andhydroxyl end groups on the polyester, depending on the ultimate end useof the composition.

An example of a useful class of polyester is the poly(alkyleneterephthalate)s. Specific examples of poly(alkylene terephthalate)sinclude, but are not limited to, poly(ethylene terephthalate) (PET),poly(1,4-butylene terephthalate) (PBT), poly(ethylene naphthanoate)(PEN), poly(butylene naphthanoate), (PBN), (polypropylene terephthalate)(PPT), polycyclohexanedimethanol terephthalate (PCT), and combinationscomprising at least one of the foregoing polyesters. Also useful arepoly(cyclohexanedimethanol terephthalate)-co-poly(ethyleneterephthalate), abbreviated as PETG wherein the polymer comprisesgreater than or equal to 50 mole % of poly(ethylene terephthalate), andabbreviated as PCTG, wherein the polymer comprises greater than 50 mole% of poly(cyclohexanedimethanol terephthalate). The above polyesters caninclude the analogous aliphatic polyesters such as poly(alkylenecyclohexanedicarboxylate), an example of which ispoly(1,4-cyclohexylenedimethylene-1,4-cyclohexanedicarboxylate) (PCCD).Also contemplated are the above polyesters with a minor amount, e.g.,from 0.5 to 10 percent by weight, of units derived from an aliphaticdiacid and/or an aliphatic polyol to make copolyesters.

The polycarbonate may also comprise a polysiloxane-polycarbonatecopolymer, also referred to as a polysiloxane-polycarbonate. Thepolysiloxane (also referred to herein as “polydiorganosiloxane”) blocksof the copolymer comprise repeating siloxane units (also referred toherein as “diorganosiloxane units”) of formula (8):

wherein each occurrence of R is same or different, and is a C₁₋₁₃monovalent organic radical. For example, R may independently be a C₁-C₁₃alkyl group, C₁-C₁₃ alkoxy group, C₂-C₁₃ alkenyl group, C₂-C₁₃alkenyloxy group, C₃-C₆ cycloalkyl group, C₃-C₆ cycloalkoxy group,C₆-C₁₄ aryl group, C₆-C₁₀ aryloxy group, C₇-C₁₃ arylalkyl group, C₇-CI₃arylalkoxy group, C₇-CI₃ alkylaryl group, or C₇-C₁₃ alkylaryloxy group.The foregoing groups may be fully or partially halogenated withfluorine, chlorine, bromine, or iodine, or a combination thereof.Combinations of the foregoing R groups may be used in the samecopolymer.

The value of D in formula (8) may vary widely depending on the type andrelative amount of each component in the thermoplastic composition, thedesired properties of the composition, and like considerations.Generally, D may have an average value of 2 to 1,000, specifically 2 to500, and more specifically 5 to 100. In one embodiment, D has an averagevalue of 10 to 75, and in still another embodiment, D has an averagevalue of 40 to 60. Where D is of a lower value, e.g., less than 40, itmay be desirable to use a relatively larger amount of thepolycarbonate-polysiloxane copolymer. Conversely, where D is of a highervalue, e.g., greater than 40, it may be necessary to use a relativelylower amount of the polycarbonate-polysiloxane copolymer.

A combination of a first and a second (or more)polysiloxane-polycarbonate copolymer may be used, wherein the averagevalue of D of the first copolymer is less than the average value of D ofthe second copolymer.

In one embodiment, the polydiorganosiloxane blocks are provided byrepeating structural units of formula (9):

wherein D is as defined above; each R may independently be the same ordifferent, and is as defined above; and each Ar may independently be thesame or different, and is a substituted or unsubstituted C₆-C₃₀ aryleneradical, wherein the bonds are directly connected to an aromatic moiety.Suitable Ar groups in formula (9) may be derived from a C₆-C₃₀dihydroxyarylene compound, for example a dihydroxyarylene compound offormula (3), (4), or (7) above. Combinations comprising at least one ofthe foregoing dihydroxyarylene compounds may also be used. Specificexamples of suitable dihydroxyarylene compounds are1,1-bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane,2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)butane,2,2-bis(4-hydroxyphenyl)octane, 1,1-bis(4-hydroxyphenyl)propane,1,1-bis(4-hydroxyphenyl) n-butane,2,2-bis(4-hydroxy-1-methylphenyl)propane,1,1-bis(4-hydroxyphenyl)cyclohexane, bis(4-hydroxyphenyl sulphide), and1,1-bis(4-hydroxy-t-butylphenyl)propane. Combinations comprising atleast one of the foregoing dihydroxy compounds may also be used.

Units of formula (9) may be derived from the corresponding dihydroxycompound of formula (10):

wherein R, Ar, and D are as described above. Compounds of formula (10)may be obtained by the reaction of a dihydroxyarylene compound with, forexample, an alpha, omega-bisacetoxypolydiorangonosiloxane under phasetransfer conditions.

In another embodiment, polydiorganosiloxane blocks comprise units offormula (11):

wherein R and D are as described above, and each occurrence of R¹ isindependently a divalent C₁-C₃₀ alkylene, and wherein the polymerizedpolysiloxane unit is the reaction residue of its corresponding dihydroxycompound. In a specific embodiment, the polydiorganosiloxane blocks areprovided by repeating structural units of formula (12):

wherein R and D are as defined above. Each R² in formula (12) isindependently a divalent C₂-C₈ aliphatic group. Each M in formula (12)may be the same or different, and may be a halogen, cyano, nitro, C₁-C₈alkylthio, C₁-C₈ alkyl, C₁-C₈ alkoxy, C₂-C₈ alkenyl, C₂-C₈ alkenyloxygroup, C₃-C₈ cycloalkyl, C₃-C₈ cycloalkoxy, C₆-C₁₀ aryl, C₆-C₁₀ aryloxy,C₇-C₁₂ arylalkyl, C₇-C₁₂ arylalkoxy, C₇-C₁₂ alkylaryl, or C₇-C₁₂alkylaryloxy, wherein each n is independently 0, 1, 2, 3, or 4.

In one embodiment, M is bromo or chloro, an alkyl group such as methyl,ethyl, or propyl, an alkoxy group such as methoxy, ethoxy, or propoxy,or an aryl group such as phenyl, chlorophenyl, or tolyl; R² is adimethylene, trimethylene or tetramethylene group; and R is a C₁₋₈alkyl, haloalkyl such as trifluoropropyl, cyanoalkyl, or aryl such asphenyl, chlorophenyl or tolyl. In another embodiment, R is methyl, or amixture of methyl and trifluoropropyl, or a mixture of methyl andphenyl. In still another embodiment, M is methoxy, n is one, R² is adivalent C₁-C₃ aliphatic group, and R is methyl.

Units of formula (12) may be derived from the corresponding dihydroxypolydiorganosiloxane (13):

wherein R, D, M, R², and n are as described above. Such dihydroxypolysiloxanes can be made by effecting a platinum catalyzed additionbetween a siloxane hydride of formula (14):

wherein R and D are as previously defined, and an aliphaticallyunsaturated monohydric phenol. Suitable aliphatically unsaturatedmonohydric phenols included, for example, eugenol, 2-allylphenol,4-allyl-2-methylphenol, 4-allyl-2-phenylphenol, 4-allyl-2-bromophenol,4-allyl-2-t-butoxyphenol, 4-phenyl-2-phenylphenol,2-methyl-4-propylphenol, 2-allyl-4,6-dimethylphenol,2-allyl-4-bromo-6-methylphenol, 2-allyl-6-methoxy-4-methylphenol and2-allyl-4,6-dimethylphenol. Mixtures comprising at least one of theforegoing may also be used.

The polysiloxane-polycarbonate may comprise 50 to 99 wt % of carbonateunits and 1 to 50 wt % siloxane units. Within this range, thepolysiloxane-polycarbonate copolymer may comprise 70 to 98 wt %,specifically 75 to 97 wt % of carbonate units and 2 to 30 wt %,specifically 3 to 25 wt % siloxane units.

In an embodiment, the polysiloxane-polycarbonate may comprisepolysiloxane units, and carbonate units derived from bisphenol A, e.g.,the dihydroxy compound of formula (3) in which each of A¹ and A² isp-phenylene and Y¹ is isopropylidene. Polysiloxane-polycarbonates mayhave a weight average molecular weight of 2,000 to 100,000, specifically5,000 to 50,000 as measured by gel permeation chromatography using acrosslinked styrene-divinyl benzene column, at a sample concentration of1 milligram per milliliter, and as calibrated with polycarbonatestandards.

The polysiloxane-polycarbonate can have a melt volume flow rate,measured at 300° C./1.2 kg, of 1 to 50 cubic centimeters per 10 minutes(cc/10 min), specifically 2 to 30 cc/10 min. Mixtures ofpolysiloxane-polycarbonates of different flow properties may be used toachieve the overall desired flow property.

The thermoplastic compositions further comprise an aromatic sulfonatecompound. Suitable aromatic sulfonate compounds include those of formula(15):(Y)_(m)—Ar—(Z—S(O)₂—X)_(n)  (15)wherein each X is independently a substituted or unsubstituted C₁-C₂₀alkyl, substituted or unsubstituted C₁-C₂₀ arylalkyl, substituted orunsubstituted C₆-C₂₀ aryl, or substituted or unsubstituted C₇-C₄₀alkylaryl. When present, the substituent on the X group can be, forexample, nitro, hydroxy, thio, halogen, or C₁-C₈ alkoxy. Examples ofsuitable X groups include, but are not limited to, methyl, ethyl,n-propyl, 2-methylpropyl, n-butyl, 2-methylbutyl, 3-methylbutyl,n-pentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, n-hexyl,cyclohexyl, n-octyl, 2-ethylhexyl, n-dodecyl, n-octadecyl n-eicosyl,camphoryl, trifluoromethyl, 2,2,2-trifluoroethyl, perfluoroethyl,perfluoro-n-butyl, perfluoro-n-hexyl, perfluoro-n-octyl,perfluorocyclohexyl, perfluoro-(4-ethylcyclohexyl)-2-ethyl, benzyl,2-methylbenzyl, 3-methylbenzyl, 4-methylbenzyl, phenyl, 2-methylphenyl,3-methylphenyl, 4-methylphenyl, 3,5-dimethylphenyl, 2,3-dimethylphenyl,2,4-dimethylphenyl, 2,5-dimethylphenyl, 2,6-dimethylphenyl,2,3,4-trimethylphenyl, 2,3,5-trimethylphenyl, 3,4,5-trimethylphenyl,2,4,6-trimethylphenyl, 4-ethylphenyl, 4-n-butylphenyl,4-tert-butylphenyl, 2-trifluoromethylphenyl, 4-trifluoromethylphenyl,4-methoxyphenyl, 4-tert-butoxyphenyl, 4-fluorophenyl, 4-chlorophenyl,4-bromophenyl, naphthyl, C₁-C₈ alkyl-substituted naphthyl, C₁-C₈ alkylether-substituted naphthyl, halogen-substituted naphthyl, and the like.

Also in formula (15), each Z is an oxygen-containing linking groupselected from —O—, or substituted or unsubstituted —(O—C₁₋₂₀—)_(w)—O—,wherein w is 1 to 20. When present, the substituent on the—(O—C₁₋₂₀—)_(w)—O— group can be, for example, nitro, hydroxy, thio,halogen, C₁-C₈ alkoxy, C₆-C₂₀ aryl, or C₆-C₂₀ aryloxy. Suitable Z groupsinclude oxygen diradical, ethanedioxy, 1,2-propanedioxy,1,3-propanedioxy, 1,2-butanedioxy, 1,3-butanedioxy, 1,4-butanedioxy,2,3-butanedioxy, 1,2-pentanedioxy, 1,3-pentanedioxy, 1,4-pentanedioxy,1,5-pentanedioxy, 2,3-pentanedioxy, 2,4-pentanedioxy,2-methyl-1,2-butanedioxy, 2-methyl-1,3-butanedioxy,2-methyl-1,4-butanedioxy, 2-methyl-2,3-butanedioxy,2,2-dimethyl-1,2-propanedioxy, 2,2-dimethyl-1,3-propanedioxy,3,3-dimethyl-1,2-propanedioxy, 1,1-dimethyl-2,3-propanedioxy,1,2-hexanedioxy, 1,3-hexanedioxy, 1,4-hexanedioxy, 1,5-hexanedioxy,1,6-hexanedioxy, 2,3-hexanedioxy, 2,4-hexanedioxy, 2,5-hexanedioxy,2-methyl-1,2-pentanedioxy, 2-methyl-1,3-pentanedioxy,2-methyl-1,4-pentanedioxy, 2-methyl-2,3-pentanedioxy,2-methyl-2,4-pentanedioxy, 2,2-dimethyl-1,2-butanedioxy,2,2-dimethyl-1,3-butanedioxy, 3,3-dimethyl-1,2-butanedioxy,1,1-dimethyl-2,3-butanedioxy, and the like; isomers of octanedioxy,decanedioxy, undecanedioxy, dodecanedioxy, hexadecanedioxy,octadecanedioxy, icosananedioxy, and docosananedioxy; and substitutedand unsubstituted cyclopropanedioxy, cyclobutanedioxy,cyclopentanedioxy, cyclohexanedioxy, 1,4-dioxymethyl cyclohexane,polyalkylenedioxy units, such as ethylenedioxy, 1,2-propylenedioxy,1,3-propylenedioxy, 1,2-butylenedioxy, 1,4-butylenedioxy,1,6-hexylenedioxy, and the like.

Also, in formula (15), Ar is a C₆-C₆₂ aromatic group. Suitable Ar groupsmay include C₆ aromatic; C₁₀ fused aromatic; C₁₄ fused aromatic; C₂₀fused aromatic; and C₂₀ or higher fused polycyclic aromatics includingiptycenes. Examples of suitable Ar groups include, but are not limitedto, benzene, naphthalene, anthracene, phenanthrene, triptycene,tetraiptycene, pentaiptycene, and the like. Also in formula (15), m is0-3 and n is 3-6. In an embodiment, Ar is C₆ aromatic group, having avalency of m+n, where m+n is 6. Where m+n is less than the number ofavailable valencies, the unspecified valences are occupied by hydrogen.The —(Z—S(O)₂—X) groups may be positioned ortho, meta, or para to eachother on the Ar group. In a specific embodiment, at least two of thegroups —(Z—S(O)₂—X) are positioned ortho to each other on a C₆ aromaticgroup. In a more specific embodiment, each —(Z—S(O)₂—X) group ispositioned ortho to at least one other —Z—S(O)₂—X) group.

Also in formula (15), each Y is independently C₁-C₂₀ alkyl, substitutedC₁-C₂₀ alkyl, C₆-C₂₀ aryl, C₁-C₈ alkyl-substituted C₆-C₂₀ aryl, halogen,nitro, C₁-C₂₀ alkoxycarbonyl, C₁-C₂₀ alkoxy, or C₁-C₂₀ acyl. Examples ofsuitable Y groups include, but are not limited to, the halogens (fluoro,chloro, bromo, iodo); alkoxycarbonyl such as methoxy carbonyl, ethylcarbonyl, t-butyl carbonyl, cyclohexyl carbonyl, phenyl carbonyl, andthe like; alkoxy groups such as —OCH₃, —OCH₂CH₃, —O-t-butyl, —O-n-butyl,—O-n-octyl, and the like; acyl groups derived from Friedel-Crafts-typeacylation of the aromatic ring including acetyl, pivaloyl, n-octyloyl,n-dodecoyl, n-stearoyl, benzoyl, and the like; alkyl groups includingmethyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl,n-pentyl, 2-pentyl, 3-pentyl, isopentyl, neopentyl, hexyl, heptyl,octyl, nonyl, decyl, dodecyl, octadecyl, cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl, cyclohexyl, adamantyl, norbornyl, and the like;and aryl groups including phenyl, C₁-C₈ alkylphenyl, C₁-C₈ alkoxyphenyl,halophenyl, and the like.

The compounds of formula (15) may be derived from the reaction of asulfonic acid or derivative thereof with a polyhydroxy-substitutedaromatic compound having at least three hydroxyl groups. Derivatives ofsulfonic acids, such as sulfonic acid halides (e.g., fluoride orchloride), anhydrides, and mixed anhydrides, are useful for effectingsulfonation of the polyhydroxy-substituted aromatic compound. Examplesof sulfonic acids that can be derivatized to useful form for preparingthe aromatic sulfonate compounds include, but are not limited to,methanesulfonic acid, ethanesulfonic acid, n-propanesulfonic acid,2-methylpropanesulfonic acid, n-butanesulfonic acid,2-methylbutanesulfonic acid, 3 methylbutanesulfonic acid,n-pentanesulfonic acid, 2-methylpentanesulfonic acid,3-methylpentanesulfonic acid, 4-methylpentanesulfonic acid,n-hexanesulfonic acid, cyclohexanesulfonic acid, n-octanesulfonic acid,2-ethylhexanesulfonic acid, n-dodecanesulfonic acid,n-octadecanesulfonic acid, n-eicosanesulfonic acid, camphorsulfonicacid, trifluoromethanesulfonic acid (also referred to as triflic acid),2,2,2-trifluoroethanesulfonic acid, perfluoroethanesulfonic acid,perfluoro-n-butanesulfonic acid, perfluoro-n-hexanesulfonic acid,perfluoro-n-octanesulfonic acid, perfluorocyclohexanesulfonic acid,perfluoro-(4-ethylcyclohexyl)-2-ethylsulfonic acid, benzenesulfonicacid, 2-methylbenzenesulfonic acid, 3-methylbenzenesulfonic acid,4-methylbenzenesulfonic acid (p-toluenesulfonic acid),3,5-dimethylbenzenesulfonic acid, 2,3-dimethylbenzenesulfonic acid,2,4-dimethylbenzenesulfonic acid, 2,5-dimethylbenzenesulfonic acid,2,6-dimethylbenzenesulfonic acid, 2,3,4-trimethylbenzenesulfonic acid,2,3,5-trimethylbenzenesulfonic acid, 3,4,5-trimethylbenzenesulfonicacid, 2,4,6-trimethylbenzenesulfonic acid, ethyl benzenesulfonic acid,butyl benzenesulfonic acid, tert-butylbenzenesulfonic acid,4-methoxybenzenesulfonic acid, 4-tert-butoxybenzenesulfonic acid,2-fluorobenzenesulfonic acid, 4-fluorobenzenesulfonic acid,4-chlorobenzenesulfonic acid, 4-bromobenzenesulfonic acid,2-trifluoromethylbenzene sulfonic acid, naphthalenesulfonic acid, alkylnaphthalenesulfonic acids, alkyloxy naphthalenesulfonic acids,halo-substituted naphthalenesulfonic acids, and the like. Of thederivatives of the foregoing, p-toluenesulfonyl chloride (also referredto as tosyl chloride), n-octanesulfonyl chloride, camphorsulfonylchloride, perfluoro-n-butanesulfonyl fluoride, perfluorobutanesulfonylchloride, methanesulfonyl chloride (also referred to as mesyl chloride),and trifluoromethanesulfonyl chloride are specifically useful.

Polyhydroxy-substituted aromatic compounds having three or more hydroxygroups may be condensed with the sulfonic acid derivative, as discussedabove, to provide an aromatic sulfonate compound of formula (15).Suitable polyhydroxy-substituted aromatic compounds include, but are notlimited to, 1,2,3-trihydroxybenzene(pyrogallol),1,2,4-trihydroxybenzene, 1,3,5-trihydroxybenzene(phloroglucinol),1-methyl-3,4,5-trihydroxybenzene, and the like. An example of aspecifically suitable polyaromatic compound is1,2,3-trihydroxybenzene(pyrogallol). Where a polyhydroxy aromaticcompound is condensed with the sulfonic acid derivative to form anaromatic sulfonate compound of formula (15), the X group of the sulfonicacid derivative may be either aliphatic or aromatic. Specific examplesof useful aromatic sulfonate compounds include, but are not limited to,pyrogallol tristosylate, pyrogallol trisbenzenesulfonate, pyrogalloltrisoctylsulfonate, and phloroglucinol tristosylate, or a combinationcomprising at least one of these.

The condensation reaction between the derivative of the sulfonic acid,and the polyhydroxyaromatic compound or polyol, may generally be carriedout in a single phase using an organic solvent, in the presence of abase; alternatively, the condensation reaction may be carried out in abiphasic reaction using an organic solvent and water, in the presence ofa base.

The aromatic sulfonate compound is used in the thermoplastic compositionin an amount effective to prevent yellowing of the polycarbonate uponirradiation, in particular exposure to gamma radiation. Effectiveamounts are readily determined by one of ordinary skill in the art, andwill vary depending upon the type of resin(s) used in the composition,the type and amount of other additives, and the intended use of thecomposition. In general, the aromatic sulfonate compound is present inthe thermoplastic composition in an amount of 0.001 to 500 millimolesper kilogram (mmol/Kg), more specifically 0.01 to 50 mmol/Kg, and evenmore specifically 0.1 to 5 mmol/kg, based on the total weight of thepolycarbonate resin and the aromatic sulfonate compound. Amounts lowerthan 0.001 mmol/Kg may not be effective, while amounts greater thanabout 500 mmol/Kg do not lead to improved stability, and/or canadversely affect the mechanical properties of the thermoplasticcomposition. In an embodiment, a masterbatch composition comprisingpolycarbonate and high levels of 5 to 500 mmol/Kg of aromatic sulfonatecomposition may be prepared, wherein the masterbatch is further combinedwith polycarbonate resin and/or other polymer to form the thermoplasticcomposition.

Alternatively, the aromatic sulfonate compound is present in an amountof 0.001 to 20 wt %, more specifically 0.01 to about 10 wt %, and evenmore specifically 0.1 to 1 wt %, based on the total weight of thepolycarbonate resin and the aromatic sulfonate compound. Amounts lowerthan 0.001 wt % may not be effective, while amounts greater than about20 wt % do not lead to improved stability, and/or can adversely affectthe mechanical properties of the thermoplastic composition. In anembodiment, a masterbatch composition comprising polycarbonate and highlevels of 1.0 to 20 wt % of aromatic sulfonate composition may beprepared, wherein the masterbatch is further combined with polycarbonateresin and/or other polymer to form the thermoplastic composition.

In an unexpected and advantageous feature, however, it has been foundthat unexpectedly small amounts of aromatic sulfonate compound areeffective to prevent yellowing upon exposure to radiation, includinggamma radiation. In one embodiment, an effective amount of aromaticsulfonate compound is 0.05 to 25 mmol/Kg, specifically 0.1 to 5 mmol/Kg,more specifically 0.2 to 3 mmol/Kg, more specifically 0.25 to 2.5mmol/kg, still more specifically 0.5 to 2 mmol/Kg, and still morespecifically 0.75 to 1.7 mmol/Kg, each based on the total weight ofpolycarbonate and aromatic sulfonate compound. The foregoing amounts maybe limited by the proviso that the total amount of aromatic sulfonatecompound does not exceed 0.5 wt % of the total weight of polycarbonateand aromatic sulfonate compound, more specifically 0.25 wt %, still morespecifically 0.2, and even more specifically 0.1 wt % of the totalweight of the polycarbonate and aromatic sulfonate compound.

Alternatively, the aromatic sulfonate compound is used in thethermoplastic composition in an amount of 0.001 to 0.25 wt %, morespecifically 0.002 to 0.2 wt %, more specifically 0.003 to 0.15 wt %,still more specifically 0.004 to 0.1 wt %, and still more specifically0.005 to 0.095 wt %, based on the total weight of the polycarbonate andaromatic sulfonate compound.

The thermoplastic composition may further comprise an ionizing radiationstabilizing additive. Exemplary ionizing radiation stabilizing additivesinclude certain aliphatic alcohols, aromatic alcohols, aliphatic diols,aliphatic ethers, esters, diketones, alkenes, thiols, thioethers andcyclic thioethers, sulfones, dihydroaromatics, diethers, nitrogencompounds, or a combination comprising at least one of the foregoing.Alcohol-based stabilizing additives may be selected from mono, di-, orpolysubstituted alcohols, and can be straight, branched, cyclic and/oraromatic. Suitable aliphatic alcohols may include alkenols with sites ofunsaturation, examples of which include 4-methyl-4-penten-2-ol,3-methyl-pentene-3-ol, 2-methyl-4-penten-2-ol,2,4-dimethyl-4-penten-2-ol, 2-phenyl-4-penten-2-ol, and 9-decen-1-ol;tertiary alcohols including 3-hydroxy-3-methyl-2-butanone,2-phenyl-2-butanol, and the like; hydroxy-substituted tertiarycycloaliphatics such as 1-hydroxy-1-methyl-cyclohexane; andhydroxymethyl aromatics having an aromatic ring with carbinolsubstituents such as a methylol group (—CH₂OH) or a more complexhydrocarbon group such as (—CRHOH) or (—CR₂OH), wherein R is straightchain C₁-C₂₀ alkyl or branched C₁-C₂₀ alkyl. Exemplary hydroxy carbinolaromatics include benzhydrol, 2-phenyl-2-butanol, 1,3-benzenedimethanol,benzyl alcohol, 4-benzyloxy-benzyl alcohol, and benzyl-benzyl alcohol.

Useful classes of ionizing radiation stabilizing additives are di- andpolyfunctional aliphatic alcohols, also referred to as aliphatic diolsand aliphatic polyols. Specifically useful are aliphatic diols offormula (16):HO—(C(A′)(A″))_(d)—S—(C(B′)(B″))_(e)—OH  (16)wherein A′, A″, B′, and B″ are each independently H or C₁-C₆ alkyl; S isC₁-C₂₀ alkyl, C₂-C₂₀ alkyleneoxy, C₃-C₆ cycloalkyl, or C₃-C₆ substitutedcycloalkyl; and d and e are each 0 or 1, with the proviso that, when dand e are each 0, S is selected such that both —OH groups are notconnected directly to a single common carbon atom.

In formula (16), A′, A″, B′, and B″ can each be independently selectedfrom H, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, t-butyl,n-pentyl, 2-pentyl, 3-pentyl, isopentyl, neopentyl, n-hexyl, 2-hexyl,3-hexyl, 2-methyl pentyl, 3-methylpentyl, 2,2-dimethylbutyl,2,3-dimethylbutyl, and the like, and a combination comprising at leastone of the foregoing alkyl groups.

Spacer group S can be selected from methanediyl, ethanediyl,1,1-ethanediyl, 1,1-propanediyl, 1,2-propanediyl, 1,3-propanediyl,2,2-propanediyl, 1,1-butanediyl, 1,2-butanediyl, 1,3-butanediyl,1,4-butanediyl, 2,2-butanediyl, 2,3-butanediyl, 1,1-pentanediyl,1,2-pentanediyl, 1,3-pentanediyl, 1,4-pentanediyl, 1,5-pentanediyl,2,2-pentanediyl, 2,3-pentanediyl, 2,4-pentanediyl, 3,3-pentanediyl,2-methyl-1,1-butanediyl, 3-methyl-31,1-butanediyl,2-methyl-1,2-butanediyl, 2-methyl-1,3-butanediyl,2-methyl-1,4-butanediyl, 2-methyl-2,2-butanediyl,2-methyl-2,3-butanediyl, 2,2-dimethyl-1,1-propanediyl,2,2-dimethyl-1,2-propanediyl, 2,2-dimethyl-1,3-propanediyl,3,3-dimethyl-1,1-propanediyl, 3,3-dimethyl-1,2-propanediyl,3,3-dimethyl-2,2-propanediyl, 1,1-dimethyl-2,3-propanediyl,3,3-dimethyl-2,2-propanediyl, 1,1-hexanediyl, 1,2-hexanediyl,1,3-hexanediyl, 1,4-hexanediyl, 1,5-hexanediyl, 1,6-hexanediyl,2,2-hexanediyl, 2,3-hexanediyl, 2,4-hexanediyl, 2,5-hexanediyl,3,3-hexanediyl, 2-methyl-1,1-pentanediyl, 3-methyl-1,1-pentanediyl,2-methyl-1,2-pentanediyl, 2-methyl-1,3-pentanediyl,2-methyl-1,4-pentanediyl, 2-methyl-2,2-pentanediyl,2-methyl-2,3-pentanediyl, 2-methyl-2,4-pentanediyl,2,2-dimethyl-1,1-butanediyl, 2,2-dimethyl-1,2-butanediyl,2,2-dimethyl-1,3-butanediyl, 3,3-dimethyl-1,1-butanediyl,3,3-dimethyl-1,2-butanediyl, 3,3-dimethyl-2,2-butanediyl,1,1-dimethyl-2,3-butanediyl, 3,3-dimethyl-2,2-butanediyl, and the like;isomers of octanediyl, decanediyl, undecanediyl, dodecanediyl,hexadecanediyl, octadecanediyl, icosananediyl, and docosananediyl; andsubstituted and unsubstituted cyclopropanediyl, cyclobutanediyl,cyclopentanediyl, cyclohexanediyl, wherein substituents may be thepoints of radical attachment, such as in 1,4-dimethylenecyclohexane, ormay include branched and straight chain alkyl, cycloalkyl, and the like.Additionally, the spacer group S may be selected from one or morediradicals comprising polyalkyleneoxy units, such as ethyleneoxy,1,2-propyleneoxy, 1,3-propyleneoxy, 1,2-butyleneoxy, 1,4-butyleneoxy,1,6-hexyleneoxy, and the like; and a combination comprising at least oneof these.

Specific examples of suitable aliphatic diols include ethylene glycol,propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol,meso-2,3-butanediol, 1,2-pentanediol, 2,3-pentanediol, 1,4-pentanediol,1,4-hexandiol, and the like; alicyclic alcohols such as1,3-cyclobutanediol, 2,2,4,4-tetramethylcyclobutanediol,1,2-cyclopentanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol,1,4-cyclohexanediol, 1,4-dimethylolcyclohexane, and the like; branchedacyclic diols such as 2,3-dimethyl-2,3-butanediol (pinacol), and2-methyl-2,4-pentanediol (hexylene glycol); andpolyalkyleneoxy-containing alcohols such as polyethylene glycol,polypropylene glycol, block or randompoly(ethyleneglycol-co-propyleneglycols), and diols of copolymerscontaining polyalkyleneoxy-groups. Useful polyols may includepolyaryleneoxy compounds such as polyhydroxystyrene; alkyl polyols suchas polyvinylalcohol, polysaccharaides, and esterified polysaccharides. Acombination comprising at least one of the foregoing may also be useful.Specifically suitable diols include 2-methyl-2,4-pentanediol (hexyleneglycol), polyethylene glycol, and polypropylene glycol.

Suitable aliphatic ethers may include alkoxy-substituted cyclic oracyclic alkanes such as, for example, 1,2-dialkoxyethanes,1,2-dialkoxypropanes, 1,3-dialkoxypropanes, alkoxycyclopentanes,alkoxycyclohexanes, and the like. Ester compounds (—COOR) may be usefulas stabilizers wherein R may be a substituted or unsubstituted, aromaticor aliphatic, hydrocarbon and the parent carboxy compound may likewisebe substituted or unsubstituted, aromatic or aliphatic, and/or mono- orpolyfunctional. When present, substituents may include, for example,C₁-C₈ alkyl, C₁-C₈ alkyl ether, C₆-C₂₀ aryl, and the like. Esters whichhave proven useful include tetrakis(methylene[3,5-di-t-butyl-4-hydroxy-hydrocinnamate])methane, 2,2′-oxamidobis(ethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate, andtriifunctional hindered phenolic ester compounds such as GOOD-RITE®3125, available from B. F. Goodrich in Cleveland Ohio.

Diketone compounds may also be used, specifically those having twocarbonyl functional groups and separated by a single intervening carbonatoms such as, for example 2,4-pentadione.

Sulfur-containing compounds, suitable for use as stabilizing additives,can include thiols, thioethers and cyclic thioethers. Thiols include,for example, 2-mercaptobenzothiazole; thioethers includedilaurylthiopropionate; and cyclic thioethers include 1,4-dithiane,1,4,8,11-tetrathiocyclotetradecane. Cyclic thioethers containing morethan one thioether group are useful, specifically those having a singleintervening carbon between two thioether groups such as in, for example,1,3-dithiane. The cyclic ring may contain oxygen or nitrogen members.

Aryl or alkyl sulfone stabilizing additives of general structureR—S(O)₂—R′ may also be used, where R and R′ comprise C₁-C₂₀ alkyl,C₆-C₂₀ aryl, C₁-C₂₀ alkoxy, C₆-C₂₀ aryloxy, substituted derivativesthereof, and the like, and wherein at least one of R or R′ is asubstituted or unsubstituted benzyl. When present, substituents mayinclude, for example, C₁-C₈ alkyl, C₁-C₈ alkyl ether, C₆-C₂₀ aryl, andthe like. An example of a specifically useful sulfone is benzylsulfone.

Alkenes may be used as stabilizing additives. Suitable alkenes mayinclude olefins of general structure RR′ C═CR′R′″ wherein R, R′, R″, andR′″ may each individually be the same or different and may be selectedfrom hydrogen, C₁-C₂₀ alkyl, C₁-C₂₀ cycloalkyl, C₁-C₂₀ alkenyl, C₁-C₂₀cycloalkenyl, C₆-C₂₀ aryl, C₆-C₂₀ arylalkyl, C₆-C₂₀ alkylaryl, C₁-C₂₀alkoxy, C₆-C₂₀ aryloxy and substituted derivatives thereof. Whenpresent, substituents may include, for example, C₁-C₈ alkyl, C₁-C₈ alkylether, C₆-C₂₀ aryl, and the like. The olefins may be acyclic, exocyclic,or endocyclic. Examples of specifically useful alkenes include1,2-diphenyl ethane, allyl phenol, 2,4-dimethyl-1-pentene, limonene,2-phenyl-2-pentene, 2,4-dimethyl-1-pentene, 1,4-diphenyl-1,3-butadiene,2-methyl-1-undecene, 1-dodecene, and the like, or a combinationcomprising at least one of the foregoing.

Hydroaromatic compounds may also be useful as stabilizing additives,including partially hydrogenated aromatics, and aromatics in combinationwith an unsaturated ring. Specific aromatics include benzene and/ornaphthalene based systems. Examples of suitable hydroaromatic compoundsinclude indane, 5,6,7,8-tetrahydro-1-naphthol,5,6,7,8-tetrahydro-2-naphthol, 9,10-dihydro anthracene,9,10-dihydrophenanthrene, 1-phenyl-1-cyclohexane,1,2,3,4-tetrahydro-1-naphthol, and the like, or a combination comprisingat least one of the foregoing.

Diethers, including hydrogenated and nonhydrogenated, and substitutedand unsubstituted pyrans, may also be used as stabilizing additives.When present, substituents may include C₁-C₈ alkyl, C₁-C₈ alkyl ether,or C₆-C₂₀ aryl. The pyrans may have substituents including C₁-C₂₀ alkyl,C₆-C₂₀ aryl, C₁-C₂₀ alkoxy, or C₆-C₂₀ aryloxy, and which may bepositioned on any carbon of the pyran ring. Specifically usefulsubstituent groups include C₁-C₂0 alkoxy or C₆-C₂₀ aryloxy, located onthe ring at the six position. Hydrogenated pyrans are specificallyuseful. Examples of suitable diethers include dihydropyranyl ethers andtetrahydropyranyl ethers.

Nitrogen compounds which may function as stabilizers include highmolecular weight oxamide phenolics, for example, 2,2-oxamido bis-[ethyl3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], high molecular weightoxalic anilides and their derivatives, and amine compounds such asthiourea.

Ionizing radiation stabilizing additives are typically used in amountsof 0.001 to 1 wt %, specifically 0.005 to 0.75 wt %, more specifically0.01 to 0.5 wt %, and still more specifically 0.05 to 0.25 wt %, basedon the total weight of the polycarbonate and aromatic sulfonatecompound. In an embodiment, a specifically suitable ionizing radiationstabilizing additive is an aliphatic diol.

The thermoplastic composition may further comprise a hydrolysisstabilizer. Typical hydrolysis stabilizers may includecarbodiimide-based additives such as aromatic and/or cycloaliphaticmonocarbo-diimides substituted in position 2 and 2′, such as2,2′,6,6′-tetraisopropyidiphenylcarbodiimide. Polycarbodiimides having amolecular weight of over 500 grams per mole are also suitable. Othercompounds useful as hydrolysis stabilizers include an epoxy modifiedacrylic oligomers or polymers, and oligomers based on cycloaliphaticepoxides. Specific examples of suitable epoxy functionalized stabilizersinclude Cycloaliphatic Epoxide Resin ERL-4221 supplied by Union CarbideCorporation (a subsidiary of Dow Chemical), Danbury, Conn.; and JONCRYL®ADR-4300 and JONCRYL® ADR-4368, available from Johnson Polymer Inc,Sturtevant, Wis. Hydrolysis stabilizers can be used in amounts of 0.001to 1 wt %, specifically 0.01 to 0.5 wt %, and more specifically 0.1 to0.3 wt %, based on the total weight of the polycarbonate and aromaticsulfonate compound.

As discussed above, when exposed to gamma radiation, polycarbonatesbecome yellowed in color, with the degree of yellowness increasing withincreasing exposure dose of the gamma radiation. At sufficiently highradiation doses, the yellow color may become sufficiently dark that anarticle prepared from the polycarbonate is compromised in itsusefulness. Likewise, with increasing gamma radiation doses,transparency decreases.

While it is not required to provide an explanation of how an inventionworks, such theories may be useful to for the purposes of better helpingthe reader to comprehend the invention. Thus, it is to be understoodthat the claims are not to be limited by the following theory ofoperation. It is believed that exposure to gamma radiation generatesfree radical breakdown products of the polycarbonate which can react toform species with extended pi-bond conjugation, and that therefore havea yellow color. Stabilizers can be included in the polycarbonate andused to stabilize or react with these radical species, thus slowing thedegradation of polycarbonates, but none appear to be sufficiently activeto completely prevent yellowing. The yellowness index of a polycarbonatehaving a prior art ionizing radiation stabilizing additive alone afterexposure to a gamma radiation dose of 83 kGy is typically greater thanabout 50, compared with a yellowness index value of less than 1 for thecomposition before exposure. Similarly, the loss in transparency of apolycarbonate stabilized in this way and treated with the same gammaradiation dose can be greater than or equal to about 15%.

The use of other types of stabilizers, such as those based on photoacidgenerators that produce sulfonic acids, in particular monofunctionalphotoacid generators or difunctional photoacid generators havingstraight-chain (i.e., unbranched) alkyl or polyether groups that producesulfonic acids (1 or 2 equivalents of acid per molecule of photoacidgenerator) have been found to require loadings of the stabilizer inexcess of 0.5% by weight of the composition. Increased amounts ofgenerated acid can lead to the formation of other breakdown products inthe polycarbonate, thus potentially causing additional degradation ofthe polycarbonate and mitigating the effectiveness of the stabilizer.Additives having aromatic or benzylic oxy and/or carbonyl groups, andwith or without alcohol functional groups present, have been includedwith such prior art mono- and di-functional photoacid generators toimprove their performance. However, the use of such additives is notdesirable for various reasons of cost, volatility, and concerns abouthandling, specifically for odor threshold and workplace exposure.Brominated compounds such as, for example, brominated bisphenol A, havealso been found to be useful for reducing yellowing of polycarbonatecompounds. However, concerns about the environmental impacts of halidessuch as bromine make this class of compounds less desirable to use. Blueand/or violet colorants have also been added to polycarbonatecompositions in order to offset the yellowness resulting from thesterilization. Compositions comprising a colorant and articles moldedfrom them may be visibly blue or violet shaded. However, colorcompensation may not be an effective strategy for obtaining colorlessparts especially as the dose of ionizing radiation is increased. Inaddition, the amount of colorant added to the resin is often selectedfor a given radiation dose, and thus variation of exposure dose due toprocess variability or re-sterilization may cause visible colordifferences between sterilized articles.

Surprisingly, it has been found that a polycarbonate and an aromaticsulfonate compound as described herein can be used to make athermoplastic composition that has significantly improved resistance toyellowing upon exposure to gamma radiation. The presence of the aromaticsulfonate compound provides a higher degree of stability in athermoplastic composition comprising polycarbonate upon exposure togamma radiation, per unit of aromatic sulfonate compound used, thanobserved with the aforementioned prior art stabilizers. A low loading ofless than 0.5 wt % of the substituted aromatic composition in thepolycarbonate composition can accomplish this. Such low loadings ofsubstitituted aromatic composition can allow the preparation ofthermoplastic compositions with low color (i.e., without added pigmentor dye) useful for making articles wherein the article has a thicknessof 3.2±0.12 millimeters and a transmission of greater than 95% accordingto ASTM D1003-00, and wherein these properties are maintained aftergamma irradiation at a total dose of up to 83 kGy.

Again without wishing to be bound by theory, it is believed that thearomatic sulfonate compounds disclosed herein generate active radicalspecies more efficiently than the prior art mono- or disubstitutedaromatic compounds, and thereby provide a higher concentration of activeradicals per unit of gamma radiation energy absorbed. Under this theory,these active radicals are believed to neutralize reactive speciesgenerated from polycarbonates, which would otherwise lead topolycarbonate degradation products that can lead to increased yellownessin the polycarbonate. Including an ionizing radiation stabilizingadditive, specifically an aliphatic diol, with the polycarbonate andaromatic sulfonate compound, can provide an additional synergisticimprovement in resistance to increase in yellowness. Further, includinga hydrolysis stabilizer having epoxy functional groups with thepolycarbonate, aromatic sulfonate compound, and aliphatic diol, canprovide yet a further improvement in resistance to an increase inyellowness. It is further believed that the presence of the hydrolysisstabilizer neutralizes additional reactive species, thereby providingthe additional stabilizing effect. The amounts and identities of thepolycarbonate, aromatic sulfonate compound, and where also included,ionizing radiation stabilizing additive and/or hydrolysis stabilizer,are selected such that the increase in the yellowness of an articlemolded from the thermoplastic composition prepared therewith isminimized after gamma radiation exposure.

The increase in yellowness of a thermoplastic composition after gammaradiation exposure may be determined by measuring the yellowness index(YI) of a molded article prepared from the thermoplastic composition,and comparing to the YI of the article before exposure. The YI of thethermoplastic composition can be measured using transmittance and/orreflective spectroscopic methods depending upon the combination oftransparency, color, and surface finish appearance of the article moldedfrom the thermoplastic composition. Where a molded article prepared fromthe thermoplastic composition is either transparent or translucent; iscolorless, white, or off-white; and is glossy, semi-glossy, ornon-glossy, the YI of the molded article may be determined according toASTM D1925-70. Where the molded article is opaque; is off-white ornon-white; and has a glossy surface finish, the YI may be determinedusing reflectance measurement according to ASTM E313-73. Generally,higher doses of ionizing radiation give larger increases in measuredyellowness index, and lower doses of ionizing radiation give smallerincreases in yellowness index. It has been observed that the increase inmeasured yellowness index in the thermoplastic compositions does notnecessarily increase linearly with increasing dose. The thermoplasticcomposition from which the article for testing is molded can containadditives including ionizing radiation stabilizing additives, and otheradditives typically included with polycarbonates, such as mold releaseagents and antioxidants, wherein the presence of these additives in anamount effective to perform the intended function does not significantlyadversely affect the desired properties of the thermoplasticcomposition. Typically, the total amount of these additives is less than1.0 percent by weight of the total weight of components present inthermoplastic composition. In an exemplary embodiment, additives presentin the thermoplastic composition used to prepare a molded article foryellowness testing may include 0.15 weight percent of2-methyl-2,4-pentanediol as aliphatic diol, 0.27 weight percentpentaerythritol tetrastearate as a mold release agent, and 0.027 weightpercent of 2,6-di-tert-butylphenyl)phosphite as an antioxidant.

Thus, in an embodiment, a molded article having a thickness of 3.2±0.12millimeters and consisting of the polycarbonate, aromatic sulfonatecompound, and an effective amount (for the purposes of this test,defined herein as less than 1.0 wt % of the total weight of the article)of each of a mold-release agent and an antioxidant has, after exposureto a total gamma radiation dose of 83 kGy and when measured according toASTM D1925-70, an increase in yellowness index (dYI) of less than orequal to 45, specifically less than or equal to 40, more specificallyless than or equal to 30, still more specifically less than or equal to20, and still more specifically less than or equal to 19, when comparedto the unexposed molded article. In an embodiment, the articleconsisting of the polycarbonate and aromatic sulfonate compound(compounded as a masterbatch), a polycarbonate resin, and themold-release agent and antioxidant has dYI values that are the same asthose of an article prepared without using a masterbatch.

In another embodiment, a molded article having a thickness of 3.2±0.12millimeters and consisting of polycarbonate, aromatic sulfonatecompound, aliphatic diol, and an effective amount of each of amold-release agent and an antioxidant has, after exposure to a totalgamma radiation dose of 83 kGy and when measured according to ASTMD1925-70, an increase in yellowness index (dYI) of less than or equal to29, specifically less than or equal to 25, more specifically less thanor equal to 23, and still more specifically less than or equal to 20,when compared to the unexposed molded article. In another embodiment, amolded article having a thickness of 3.2±0.12 millimeters and consistingof polycarbonate, aromatic sulfonate compound, aliphatic diol, and aneffective amount of each of a mold-release agent and an antioxidant has,after exposure to a total gamma radiation dose of 59 kGy and whenmeasured according to ASTM D1925-70, an increase in yellowness index(dYI) of less than or equal to 9, specifically less than or equal to8.5, more specifically less than or equal to 8, and still morespecifically less than or equal to 7.5, when compared to the unexposedmolded article. In another embodiment, a molded article having athickness of 3.2±0.12 millimeters and consisting of polycarbonate,aromatic sulfonate compound, aliphatic diol, and an effective amount ofeach of a mold-release agent and an antioxidant has, after exposure to atotal gamma radiation dose of 32 kGy and when measured according to ASTMD1925-70, an increase in yellowness index (dYI) of less than or equal to5, specifically less than or equal to 4.8, more specifically less thanor equal to 4.5, and still more specifically less than or equal to 4.3,when compared to the unexposed molded article.

In another embodiment, a molded article having a thickness of 3.2±0.12millimeters and consisting of polycarbonate, aromatic sulfonatecompound, aliphatic diol, hydrolysis stabilizer, and an effective amountof each of a mold-release agent and an antioxidant has, after exposureto a total gamma radiation dose of 83 kGy and when measured according toASTM D1925-70, an increase in yellowness index (dYI) of less than orequal to 35, specifically less than or equal to 30, more specificallyless than or equal to 20, and still more specifically less than or equalto 15, when compared to the unexposed molded article. In anotherembodiment, a molded article having a thickness of 3.2±0.12 millimetersand consisting of polycarbonate, aromatic sulfonate compound, aliphaticdiol, hydrolysis stabilizer, and an effective amount of each of amold-release agent and an antioxidant has, after exposure to a totalgamma radiation dose of 51 kGy and when measured according to ASTMD1925-70, an increase in yellowness index (dYI) of less than or equal to13, specifically less than or equal to 10, more specifically less thanor equal to 9, and still more specifically less than or equal to 8, whencompared to the unexposed molded article.

In addition to the polycarbonate, other resins, aromatic sulfonatecompound, and where desired, ionizing radiation stabilizing additiveand/or hydrolysis stabilizer, the thermoplastic composition may includevarious other additives ordinarily incorporated with thermoplasticcompositions of this type, with the proviso that the additives areselected so as not to adversely affect the desired properties of thethermoplastic composition. Mixtures of additives may be used. Suchadditives may be mixed at a suitable time during the mixing of thecomponents for forming the thermoplastic composition.

The thermoplastic composition may comprise a colorant such as a pigmentand/or dye additive. Suitable pigments include for example, inorganicpigments such as metal oxides and mixed metal oxides such as zinc oxide,titanium dioxides, iron oxides or the like; sulfides such as zincsulfides, or the like; aluminates; sodium sulfo-silicates, sulfates,chromates, or the like; carbon blacks; zinc ferrites; ultramarine blue;Pigment Brown 24; Pigment Red 101; Pigment Yellow 119; organic pigmentssuch as azos, di-azos, quinacridones, perylenes, naphthalenetetracarboxylic acids, flavanthrones, isoindolinones,tetrachloroisoindolinones, anthraquinones, anthanthrones, dioxazines,phthalocyanines, and azo lakes; Pigment Blue 60, Pigment Red 122,Pigment Red 149, Pigment Red 177, Pigment Red 179, Pigment Red 202,Pigment Violet 29, Pigment Blue 15, Pigment Blue 15:4, Pigment Blue 28,Pigment Green 7, Pigment Yellow 147 and Pigment Yellow 150, orcombinations comprising at least one of the foregoing pigments. Pigmentscan be used in amounts of 0.01 to 10 percent by weight, based on thetotal weight of the polycarbonate and aromatic sulfonate compound.

Suitable dyes can be organic materials and include, for example,coumarin dyes such as coumarin 460 (blue), coumarin 6 (green), nile redor the like; lanthanide complexes; hydrocarbon and substitutedhydrocarbon dyes; polycyclic aromatic hydrocarbon dyes; scintillationdyes such as oxazole or oxadiazole dyes; aryl- or heteroaryl-substitutedpoly (C₂₋₈) olefin dyes; carbocyanine dyes; indanthrone dyes;phthalocyanine dyes; oxazine dyes; carbostyryl dyes;napthalenetetracarboxylic acid dyes; porphyrin dyes; bis(styryl)biphenyldyes; acridine dyes; anthraquinone dyes; cyanine dyes; methine dyes;arylmethane dyes; azo dyes; indigoid dyes, thioindigoid dyes, diazoniumdyes; nitro dyes; quinone imine dyes; aminoketone dyes; tetrazoliumdyes; thiazole dyes; perylene dyes, perinone dyes;bis-benzoxazolylthiophene (BBOT); triarylmethane dyes; xanthene dyes;thioxanthene dyes; naphthalimide dyes; lactone dyes; fluorophores suchas anti-stokes shift dyes which absorb in the near infrared wavelengthand emit in the visible wavelength, or the like; luminescent dyes suchas 7-amino-4-methylcoumarin;3-(2′-benzothiazolyl)-7-diethylaminocoumarin;2-(4-biphenylyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole;2,5-bis-(4-biphenylyl)-oxazole; 2,2′-dimethyl-p-quaterphenyl;2,2-dimethyl-p-terphenyl; 3,5,3″″,5″″-tetra-t-butyl-p-quinquephenyl;2,5-diphenylfuran; 2,5-diphenyloxazole; 4,4′-diphenylstilbene;4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran;1,1′-diethyl-2,2′-carbocyanine iodide;3,3′-diethyl-4,4′,5,5′-dibenzothiatricarbocyanine iodide;7-dimethylamino-1-methyl-4-methoxy-8-azaquinolone-2;7-dimethylamino-4-methylquinolone-2;2-(4-(4-dimethylaminophenyl)-1,3-butadienyl)-3-ethylbenzothiazoliumperchlorate; 3-diethylamino-7-diethyliminophenoxazonium perchlorate;2-(1-naphthyl)-5-phenyloxazole; 2,2′-p-phenylen-bis(5-phenyloxazole);rhodamine 700; rhodamine 800; pyrene; chrysene; rubrene; coronene, orthe like, or combinations comprising at least one of the foregoing dyes.Where it is desirable to use organic dyes and pigments, the dyes may bescreened to determine their sensitivity to gamma radiation at a givenexposure dose or range of exposure doses. Dyes can be used in amounts of0.01 to 10 percent by weight, based on the total weight of thepolycarbonate and aromatic sulfonate compound.

The thermoplastic composition may include an impact modifier to increaseits impact resistance, where the impact modifier is present in an amountthat does not adversely affect the desired properties of thethermoplastic composition. These impact modifiers includeelastomer-modified graft copolymers comprising (i) an elastomeric (i.e.,rubbery) polymer substrate having a Tg less than 10° C., morespecifically less than −10° C., or more specifically −40° to −80° C.,and (ii) a rigid polymeric superstrate grafted to the elastomericpolymer substrate. As is known, elastomer-modified graft copolymers maybe prepared by first providing the elastomeric polymer, thenpolymerizing the constituent monomer(s) of the rigid phase in thepresence of the elastomer to obtain the graft copolymer. The grafts maybe attached as graft branches or as shells to an elastomer core. Theshell may merely physically encapsulate the core, or the shell may bepartially or essentially completely grafted to the core.

Suitable materials for use as the elastomer phase include, for example,conjugated diene rubbers; copolymers of a conjugated diene with lessthan 50 wt % of a copolymerizable monomer; olefin rubbers such asethylene propylene copolymers (EPR) or ethylene-propylene-diene monomerrubbers (EPDM); ethylene-vinyl acetate rubbers; silicone rubbers;elastomeric C₁₋₈ alkyl (meth)acrylates; elastomeric copolymers of C₁₋₈alkyl (meth)acrylates with butadiene and/or styrene; or combinationscomprising at least one of the foregoing elastomers.

Suitable conjugated diene monomers for preparing the elastomer phase areof formula (17):

wherein each X^(b) is independently hydrogen, C₁-C₅ alkyl, or the like.Examples of conjugated diene monomers that may be used are butadiene,isoprene, 1,3-heptadiene, methyl-1,3-pentadiene,2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-pentadiene; 1,3- and2,4-hexadienes, and the like, as well as mixtures comprising at leastone of the foregoing conjugated diene monomers. Specific conjugateddiene homopolymers include polybutadiene and polyisoprene.

Copolymers of a conjugated diene rubber may also be used, for examplethose produced by aqueous radical emulsion polymerization of aconjugated diene and one or more monomers copolymerizable therewith.Vinyl aromatic compounds may be copolymerized with the ethylenicallyunsaturated nitrile monomer to forma a copolymer, wherein thevinylaromatic compounds can include monomers of formula (18):

wherein each X^(c) is independently hydrogen, C₁-C₁₂ alkyl, C₃-C₁₂cycloalkyl, C₆-C₁₂ aryl, C₇-C₁₂ arylalkyl, C₇-C₁₂ alkylaryl, C₁-C₁₂alkoxy, C₃-C₁₂ cycloalkoxy, C₆-C₁₂ aryloxy, chloro, bromo, or hydroxy,and R is hydrogen, C₁-C₅ alkyl, bromo, or chloro. Examples of suitablemonovinylaromatic monomers that may be used include styrene,3-methylstyrene, 3,5-diethylstyrene, 4-n-propylstyrene,alpha-methylstyrene, alpha-methyl vinyltoluene, alpha-chlorostyrene,alpha-bromostyrene, dichlorostyrene, dibromostyrene,tetra-chlorostyrene, and the like, and combinations comprising at leastone of the foregoing compounds. Styrene and/or alpha-methylstyrene maybe used as monomers copolymerizable with the conjugated diene monomer.

Other monomers that may be copolymerized with the conjugated diene aremonovinylic monomers such as itaconic acid, acrylamide, N-substitutedacrylamide or methacrylamide, maleic anhydride, maleimide, N-alkyl-,aryl-, or haloaryl-substituted maleimide, glycidyl (meth)acrylates, andmonomers of the generic formula (19):

wherein R is hydrogen, C₁-C₅ alkyl, bromo, or chloro, and X^(c) isC₁-C₁₂ alkoxycarbonyl, C₁-C₁₂ aryloxycarbonyl, hydroxy carbonyl, or thelike. Examples of monomers of formula (17) include, acrylic acid, methyl(meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl(meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate,2-ethylhexyl (meth)acrylate, and the like, and combinations comprisingat least one of the foregoing monomers. Monomers such as n-butylacrylate, ethyl acrylate, and 2-ethylhexyl acrylate are commonly used asmonomers copolymerizable with the conjugated diene monomer. Mixtures ofthe foregoing monovinyl monomers and monovinylaromatic monomers may alsobe used.

Suitable (meth)acrylate monomers suitable for use as the elastomericphase may be cross-linked, particulate emulsion homopolymers orcopolymers of C₁₋₈ alkyl (meth)acrylates, in particular C₄₋₆ alkylacrylates, for example n-butyl acrylate, t-butyl acrylate, n-propylacrylate, isopropyl acrylate, 2-ethylhexyl acrylate, and the like, andcombinations comprising at least one of the foregoing monomers. The C₁₋₈alkyl (meth)acrylate monomers may optionally be polymerized in admixturewith up to 15 wt % of comonomers of formulas (17), (18), or (19).Exemplary comonomers include but are not limited to butadiene, isoprene,styrene, methyl methacrylate, phenyl methacrylate, penethylmethacrylate,N-cyclohexylacrylamide, vinyl methyl ether, and mixtures comprising atleast one of the foregoing comonomers. Optionally, up to 5 wt % apolyfunctional crosslinking comonomer may be present, for exampledivinylbenzene, alkylenediol di(meth)acrylates such as glycolbisacrylate, alkylenetriol tri(meth)acrylates, polyesterdi(meth)acrylates, bisacrylamides, triallyl cyanurate, triallylisocyanurate, allyl (meth)acrylate, diallyl maleate, diallyl fumarate,diallyl adipate, triallyl esters of citric acid, triallyl esters ofphosphoric acid, and the like, as well as combinations comprising atleast one of the foregoing crosslinking agents.

The elastomer phase may be polymerized by mass, emulsion, suspension,solution or combined processes such as bulk-suspension, emulsion-bulk,bulk-solution or other techniques, using continuous, semibatch, or batchprocesses. The particle size of the elastomer substrate is not critical.For example, an average particle size of 0.001 to 25 micrometers,specifically 0.01 to 15 micrometers, or even more specifically 0.1 to 8micrometers may be used for emulsion based polymerized rubber lattices.A particle size of 0.5 to 10 micrometers, specifically 0.6 to 1.5micrometers may be used for bulk polymerized rubber substrates. Particlesize may be measured by simple light transmittance methods or capillaryhydrodynamic chromatography (CHDF). The elastomer phase may be aparticulate, moderately cross-linked conjugated butadiene or C₄₋₆ alkylacrylate rubber, and preferably has a gel content greater than 70 wt %.Also suitable are mixtures of butadiene with styrene and/or C₄₋₆ alkylacrylate rubbers.

The elastomeric phase may provide 5 to 95 wt % of the total graftcopolymer, more specifically 20 to 90 wt %, and even more specifically40 to 85 wt % of the elastomer-modified graft copolymer, the remainderbeing the rigid graft phase.

The rigid phase of the elastomer-modified graft copolymer may be formedby graft polymerization of a mixture comprising a monovinylaromaticmonomer and optionally one or more comonomers in the presence of one ormore elastomeric polymer substrates. The above-describedmonovinylaromatic monomers of formula (18) may be used in the rigidgraft phase, including styrene, alpha-methyl styrene, halostyrenes suchas dibromostyrene, vinyltoluene, vinylxylene, butylstyrene,para-hydroxystyrene, methoxystyrene, or the like, or combinationscomprising at least one of the foregoing monovinylaromatic monomers.Suitable comonomers include, for example, the above-describedmonovinylic monomers and/or monomers of the general formula (19). In oneembodiment, R is hydrogen or C₁-C₂ alkyl, and X^(c) is cyano or C₁-C₁₂alkoxycarbonyl. Specific examples of suitable comonomers for use in therigid phase include, methyl (meth)acrylate, ethyl (meth)acrylate,n-propyl (meth)acrylate, isopropyl (meth)acrylate, and the like, andcombinations comprising at least one of the foregoing comonomers.

The relative ratio of monovinylaromatic monomer and comonomer in therigid graft phase may vary widely depending on the type of elastomersubstrate, type of monovinylaromatic monomer(s), type of comonomer(s),and the desired properties of the impact modifier. The rigid phase maygenerally comprise up to 100 wt % of monovinyl aromatic monomer,specifically 30 to 100 wt %, more specifically 50 to 90 wt %monovinylaromatic monomer, with the balance being comonomer(s).

Depending on the amount of elastomer-modified polymer present, aseparate matrix or continuous phase of ungrafted rigid polymer orcopolymer may be simultaneously obtained along with theelastomer-modified graft copolymer. Typically, such impact modifierscomprise 40 to 95 wt % elastomer-modified graft copolymer and 5 to 65 wt% graft (co)polymer, based on the total weight of the impact modifier.In another embodiment, such impact modifiers comprise 50 to 85 wt %,more specifically 75 to 85 wt % rubber-modified graft copolymer,together with 15 to 50 wt %, more specifically 15 to 25 wt % graft(co)polymer, based on the total weight of the impact modifier.

Another specific type of elastomer-modified impact modifier comprisesstructural units derived from at least one silicone rubber monomer, abranched acrylate rubber monomer having the formulaH₂C═C(R^(d))C(O)OCH₂CH₂R^(e), wherein R^(d) is hydrogen or a C₁-C₈linear or branched alkyl group and R^(e) is a branched C₃-C₁₆ alkylgroup; a first graft link monomer; a polymerizable alkenyl-containingorganic material; and a second graft link monomer. The silicone rubbermonomer may comprise, for example, a cyclic siloxane, tetraalkoxysilane,trialkoxysilane, (acryloxy)alkoxysilane, (mercaptoalkyl)alkoxysilane,vinylalkoxysilane, or allylalkoxysilane, alone or in combination, e.g.,decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane,trimethyltriphenylcyclotrisiloxane,tetramethyltetraphenylcyclotetrasiloxane,tetramethyltetravinylcyclotetrasiloxane, octaphenylcyclotetrasiloxane,octamethylcyclotetrasiloxane and/or tetraethoxysilane.

Exemplary branched acrylate rubber monomers include iso-octyl acrylate,6-methyloctyl acrylate, 7-methyloctyl acrylate, 6-methylheptyl acrylate,and the like, alone or in combination. The polymerizable,alkenyl-containing organic material may be, for example, a monomer offormula (18) or (19), e.g., styrene, alpha-methylstyrene, or anunbranched (meth)acrylate such as methyl methacrylate, 2-ethylhexylmethacrylate, methyl acrylate, ethyl acrylate, n-propyl acrylate, or thelike, alone or in combination.

The at least one first graft link monomer may be an(acryloxy)alkoxysilane, a (mercaptoalkyl)alkoxysilane, avinylalkoxysilane, or an allylalkoxysilane, alone or in combination,e.g., (gamma-methacryloxypropyl) (dimethoxy)methylsilane and/or(3-mercaptopropyl)trimethoxysilane. The at least one second graft linkmonomer is a polyethylenically unsaturated compound having at least oneallyl group, such as allyl methacrylate, triallyl cyanurate, or triallylisocyanurate, alone or in combination.

The silicone-acrylate impact modifier compositions can be prepared byemulsion polymerization, wherein, for example at least one siliconerubber monomer is reacted with at least one first graft link monomer ata temperature from 30° C. to 110° C. to form a silicone rubber latex, inthe presence of a surfactant such as dodecylbenzenesulfonic acid.Alternatively, a cyclic siloxane such as cyclooctamethyltetrasiloxaneand tetraethoxyorthosilicate may be reacted with a first graft linkmonomer such as (gamma-methacryloxypropyl) methyldimethoxysilane, toafford silicone rubber having an average particle size from 100nanometers to 2 micrometers. At least one branched acrylate rubbermonomer is then polymerized with the silicone rubber particles,optionally in presence of a cross linking monomer, such asallylmethacrylate in the presence of a free radical generatingpolymerization catalyst such as benzoyl peroxide. This latex is thenreacted with a polymerizable alkenyl-containing organic material and asecond graft link monomer. The latex particles of the graftsilicone-acrylate rubber hybrid may be separated from the aqueous phasethrough coagulation (by treatment with a coagulant) and dried to a finepowder to produce the silicone-acrylate rubber impact modifiercomposition. This method can be generally used for producing thesilicone-acrylate impact modifier having a particle size from 100nanometers to 2 micrometers.

Processes known for the formation of the foregoing elastomer-modifiedgraft copolymers include mass, emulsion, suspension, and solutionprocesses, or combined processes such as bulk-suspension, emulsion-bulk,bulk-solution or other techniques, using continuous, semibatch, or batchprocesses.

The foregoing types of impact modifiers, including SAN copolymers, canbe prepared by an emulsion polymerization process that is free of basicmaterials such as alkali metal salts of C₆₋₃₀ fatty acids, for examplesodium stearate, lithium stearate, sodium oleate, potassium oleate, andthe like; alkali metal carbonates, amines such as dodecyl dimethylamine, dodecyl amine, and the like; and ammonium salts of amines. Suchmaterials are commonly used as surfactants in emulsion polymerization,and may catalyze transesterification and/or degradation ofpolycarbonates. Instead, ionic sulfate, sulfonate or phosphatesurfactants may be used in preparing the impact modifiers, particularlythe elastomeric substrate portion of the impact modifiers. Suitablesurfactants include, for example, C₁₋₂₂ alkyl or C₇₋₂₅ alkylarylsulfonates, C₁₋₂₂ alkyl or C₇₋₂₅ alkylaryl sulfates, C₁₋₂₂ alkyl orC₇₋₂₅ alkylaryl phosphates, substituted silicates, and mixtures thereof.A specific surfactant is a C₆₋₁₆, specifically a C₈₋₁₂ alkyl sulfonate.In the practice, any of the above-described impact modifiers may be usedproviding it is free of the alkali metal salts of fatty acids, alkalimetal carbonates and other basic materials.

A specific impact modifier of this type is a methylmethacrylate-butadiene-styrene (MBS) impact modifier wherein thebutadiene substrate is prepared using above-described sulfonates,sulfates, or phosphates as surfactants. Other examples ofelastomer-modified graft copolymers besides ABS and MBS include but arenot limited to acrylonitrile-styrene-butyl acrylate (ASA), methylmethacrylate-acrylonitrile-butadiene-styrene (MABS), andacrylonitrile-ethylene-propylene-diene-styrene (AES). When present,impact modifiers can be present in the thermoplastic composition inamounts of 0.1 to 30 percent by weight, based on the total weight of thepolycarbonate and aromatic sulfonate compound.

The thermoplastic composition may include fillers or reinforcing agents.The fillers and reinforcing agents may desirably be in the form ofnanoparticles, i.e., particles with a median particle size (D₅₀) smallerthan 100 nm as determined using light scattering methods. Where used,suitable fillers or reinforcing agents include, for example, silicatesand silica powders such as aluminum silicate (mullite), syntheticcalcium silicate, zirconium silicate, fused silica, crystalline silicagraphite, natural silica sand, or the like; boron powders such asboron-nitride powder, boron-silicate powders, or the like; oxides suchas TiO₂, aluminum oxide, magnesium oxide, or the like; calcium sulfate(as its anhydride, dihydrate or trihydrate); calcium carbonates such aschalk, limestone, marble, synthetic precipitated calcium carbonates, orthe like; talc, including fibrous, modular, needle shaped, lamellartalc, or the like; wollastonite; surface-treated wollastonite; glassspheres such as hollow and solid glass spheres, silicate spheres,cenospheres, aluminosilicate (armospheres), or the like; kaolin,including hard kaolin, soft kaolin, calcined kaolin, kaolin comprisingvarious coatings known in the art to facilitate compatibility with thepolymeric matrix resin, or the like; single crystal fibers or “whiskers”such as silicon carbide, alumina, boron carbide, iron, nickel, copper,or the like; fibers (including continuous and chopped fibers) such asasbestos, carbon fibers, glass fibers, such as E, A, C, ECR, R, S, D, orNE glasses, or the like; sulfides such as molybdenum sulfide, zincsulfide or the like; barium compounds such as barium titanate, bariumferrite, barium sulfate, heavy spar, or the like; metals and metaloxides such as particulate or fibrous aluminum, bronze, zinc, copper andnickel or the like; flaked fillers such as glass flakes, flaked siliconcarbide, aluminum diboride, aluminum flakes, steel flakes or the like;fibrous fillers, for example short inorganic fibers such as thosederived from blends comprising at least one of aluminum silicates,aluminum oxides, magnesium oxides, and calcium sulfate hemihydrate orthe like; natural fillers and reinforcements, such as wood flourobtained by pulverizing wood, fibrous products such as cellulose,cotton, sisal, jute, starch, cork flour, lignin, ground nut shells,corn, rice grain husks or the like; organic fillers such aspolytetrafluoroethylene; reinforcing organic fibrous fillers formed fromorganic polymers capable of forming fibers such as poly(ether ketone),polyimide, polybenzoxazole, poly(phenylene sulfide), polyesters,polyethylene, aromatic polyamides, aromatic polyimides, polyetherimides,polytetrafluoroethylene, acrylic resins, poly(vinyl alcohol) or thelike; as well as additional fillers and reinforcing agents such as mica,clay, feldspar, flue dust, fillite, quartz, quartzite, perlite, tripoli,diatomaceous earth, carbon black, or the like, or combinationscomprising at least one of the foregoing fillers or reinforcing agents.

The fillers and reinforcing agents may be coated with a layer ofmetallic material to facilitate conductivity, or surface treated withsilanes to improve adhesion and dispersion with the polymeric matrixresin. In addition, the reinforcing fillers may be provided in the formof monofilament or multifilament fibers and may be used either alone orin combination with other types of fiber, through, for example,co-weaving or core/sheath, side-by-side, orange-type or matrix andfibril constructions, or by other methods known to one skilled in theart of fiber manufacture. Suitable cowoven structures include, forexample, glass fiber-carbon fiber, carbon fiber-aromatic polyimide(aramid) fiber, and aromatic polyimide fiberglass fiber or the like.Fibrous fillers may be supplied in the form of, for example, rovings,woven fibrous reinforcements, such as 0-90 degree fabrics or the like;non-woven fibrous reinforcements such as continuous strand mat, choppedstrand mat, tissues, papers and felts or the like; or three-dimensionalreinforcements such as braids. Fillers can be used in amounts of 0 to 90percent by weight, based on the total weight of the polycarbonate andaromatic sulfonate compound.

Suitable antioxidant additives include, for example, organophosphitessuch as tris(nonyl phenyl)phosphite,tris(2,4-di-t-butylphenyl)phosphite,bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, distearylpentaerythritol diphosphite or the like; alkylated monophenols orpolyphenols; alkylated reaction products of polyphenols with dienes,such astetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane,or the like; butylated reaction products of para-cresol ordicyclopentadiene; alkylated hydroquinones; hydroxylated thiodiphenylethers; alkylidene-bisphenols; benzyl compounds; esters ofbeta-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid with monohydricor polyhydric alcohols; esters ofbeta-(5-tert-butyl-4-hydroxy-3-methylphenyl)-propionic acid withmonohydric or polyhydric alcohols; esters of thioalkyl or thioarylcompounds such as distearylthiopropionate, dilaurylthiopropionate,ditridecylthiodipropionate,octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,pentaerythrityl-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionateor the like; amides ofbeta-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid or the like, orcombinations comprising at least one of the foregoing antioxidants.Antioxidants can be used in amounts of 0.0001 to 1 percent by weight,based on the total weight of the polycarbonate and aromatic sulfonatecompound.

Suitable heat stabilizer additives include, for example,organophosphites such as triphenyl phosphite,tris-(2,6-dimethylphenyl)phosphite, tris-(mixed mono-anddi-nonylphenyl)phosphite or the like; phosphonates such asdimethylbenzene phosphonate or the like, phosphates such as trimethylphosphate, or the like, or combinations comprising at least one of theforegoing heat stabilizers. Heat stabilizers can be used in amounts of0.0001 to 1 percent by weight, based on the total weight of thepolycarbonate and aromatic sulfonate compound.

Light stabilizers and/or ultraviolet light (UV) absorbing additives mayalso be used. Suitable light stabilizer additives include, for example,benzotriazoles such as 2-(2-hydroxy-5-methylphenyl)benzotriazole,2-(2-hydroxy-5-tert-octylphenyl)-benzotriazole and 2-hydroxy-4-n-octoxybenzophenone, or the like, or combinations comprising at least one ofthe foregoing light stabilizers. Light stabilizers can be used inamounts of 0.0001 to 1 percent by weight, based on the total weight ofthe polycarbonate and aromatic sulfonate compound.

Suitable UV absorbing additives include for example,hydroxybenzophenones; hydroxybenzotriazoles; hydroxybenzotriazines;cyanoacrylates; oxanilides; benzoxazinones;2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)-phenol (CYASORB®5411); 2-hydroxy-4-n-octyloxybenzophenone (CYASORB® 531);2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-(octyloxy)-phenol(CYASORB® 1164); 2,2′-(1,4-phenylene)bis(4H-3,1-benzoxazin-4-one)(CYASORB® UV-3638);1,3-bis[(2-cyano-3,3-diphenylacryloyl)oxy]-2,2-bis[[(2-cyano-3,3-diphenylacryloyl)oxy]methyl]propane(UVINUL® 3030); 2,2′-(1,4-phenylene)bis(4H-3, 1-benzoxazin-4-one);1,3-bis[(2-cyano-3,3-diphenylacryloyl)oxy]-2,2-bis[[(2-cyano-3,3-diphenylacryloyl)oxy]methyl]propane;nano-size inorganic materials such as titanium oxide, cerium oxide, andzinc oxide, all with particle size less than 100 nanometers; or thelike, or combinations comprising at least one of the foregoing UVabsorbers. UV absorbers can be used in amounts of 0.0001 to 1 percent byweight, based on the total weight of the polycarbonate and aromaticsulfonate compound.

Plasticizers, lubricants, and/or mold release agents additives may alsobe used. There is considerable overlap among these types of materials,which include, for example, phthalic acid esters such asdioctyl-4,5-epoxy-hexahydrophthalate;tris-(octoxycarbonylethyl)isocyanurate; tristearin; di- orpolyfunctional aromatic phosphates such as resorcinol tetraphenyldiphosphate (RDP), the bis(diphenyl) phosphate of hydroquinone and thebis(diphenyl) phosphate of bisphenol-A; poly-alpha-olefins; epoxidizedsoybean oil; silicones, including silicone oils; esters, for example,fatty acid esters such as alkyl stearyl esters, e.g., methyl stearate;stearyl stearate, pentaerythritol tetrastearate, and the like; mixturesof methyl stearate and hydrophilic and hydrophobic nonionic surfactantscomprising polyethylene glycol polymers, polypropylene glycol polymers,and copolymers thereof, e.g., methyl stearate andpolyethylene-polypropylene glycol copolymers in a suitable solvent;waxes such as beeswax, montan wax, paraffin wax or the like. Suchmaterials can be used in amounts of 0.001 to 1 percent by weight,specifically 0.01 to 0.75 percent by weight, more specifically 0.1 to0.5 percent by weight, based on the total weight of the polycarbonateand aromatic sulfonate compound.

The term “antistatic agent” refers to monomeric, oligomeric, orpolymeric materials that can be processed into polymer resins and/orsprayed onto materials or articles to improve conductive properties andoverall physical performance. Examples of monomeric antistatic agentsinclude glycerol monostearate, glycerol distearate, glyceroltristearate, ethoxylated amines, primary, secondary and tertiary amines,ethoxylated alcohols, alkyl sulfates, alkylarylsulfates,alkylphosphates, alkylaminesulfates, alkyl sulfonate salts such assodium stearyl sulfonate, sodium dodecylbenzenesulfonate or the like,quaternary ammonium salts, quaternary ammonium resins, imidazolinederivatives, sorbitan esters, ethanolamides, betaines, or the like, orcombinations comprising at least one of the foregoing monomericantistatic agents.

Exemplary polymeric antistatic agents include certain polyesteramidespolyether-polyamide (polyetheramide) block copolymers,polyetheresteramide block copolymers, polyetheresters, or polyurethanes,each containing polyalkylene glycol moieties polyalkylene oxide unitssuch as polyethylene glycol, polypropylene glycol, polytetramethyleneglycol, and the like. Such polymeric antistatic agents are commerciallyavailable, for example Pelestat® 6321 (Sanyo) or Pebax® MH1657(Atofina), Irgastat® P18 and P22 (Ciba-Geigy). Other polymeric materialsthat may be used as antistatic agents are inherently conducting polymerssuch as polyaniline (commercially available as PANIPOL® EB fromPanipol), polypyrrole, and polythiophenes such as for examplepoly(3,4-ethylenedioxythiophene) (commercially available from H. C.Stark), which retain some of their intrinsic conductivity after meltprocessing at elevated temperatures. In one embodiment, carbon fibers,carbon nanofibers, carbon nanotubes, carbon black, or any combination ofthe foregoing may be used in a polymeric resin containing chemicalantistatic agents to render the composition electrostaticallydissipative. Antistatic agents can be used in amounts of 0.0001 to 5percent by weight, based on the total weight of the polycarbonate andaromatic sulfonate compound.

Suitable flame retardant that may be added may be organic compounds thatinclude phosphorus, bromine, and/or chlorine. Non-brominated andnon-chlorinated phosphorus-containing flame retardants may be preferredin certain applications for regulatory reasons, for example organicphosphates and organic compounds containing phosphorus-nitrogen bonds.

One type of exemplary organic phosphate is an aromatic phosphate of theformula (GO)₃P═O, wherein each G is independently an alkyl, cycloalkyl,aryl, alkylaryl, or arylalkyl group, provided that at least one G is anaromatic group. Two of the G groups may be joined together to provide acyclic group, for example, diphenyl pentaerythritol diphosphate. Othersuitable aromatic phosphates may be, for example, phenyl bis(dodecyl)phosphate, phenyl bis(neopentyl) phosphate, phenylbis(3,5,5′-trimethylhexyl) phosphate, ethyl diphenyl phosphate,2-ethylhexyl di(p-tolyl)phosphate, bis(2-ethylhexyl)p-tolyl phosphate,tritolyl phosphate, bis(2-ethylhexyl)phenyl phosphate,tri(nonylphenyl)phosphate, bis(dodecyl)p-tolyl phosphate, dibutyl phenylphosphate, 2-chloroethyl diphenyl phosphate, p-tolylbis(2,5,5′-trimethylhexyl)phosphate, 2-ethylhexyl diphenyl phosphate, orthe like. A specific aromatic phosphate is one in which each G isaromatic, for example, triphenyl phosphate, tricresyl phosphate,isopropylated triphenyl phosphate, and the like.

Di- or polyfunctional aromatic phosphorus-containing compounds are alsouseful, for example, compounds of the formulas below:

wherein each G¹ is independently a hydrocarbon having 1 to 30 carbonatoms; each G² is independently a hydrocarbon or hydrocarbonoxy having 1to 30 carbon atoms; each X^(a) is independently a hydrocarbon having 1to 30 carbon atoms; each X is independently a bromine or chlorine; m is0 to 4, and n is 1 to 30. Examples of suitable di- or polyfunctionalaromatic phosphorus-containing compounds include resorcinol tetraphenyldiphosphate (RDP), the bis(diphenyl)phosphate of hydroquinone and thebis(diphenyl)phosphate of bisphenol-A, respectively, their oligomericand polymeric counterparts, and the like.

Exemplary suitable flame retardant compounds containingphosphorus-nitrogen bonds include phosphonitrilic chloride, phosphorusester amides, phosphoric acid amides, phosphonic acid amides, phosphinicacid amides, tris(aziridinyl)phosphine oxide. When present,phosphorus-containing flame retardants can be present in amounts of 0.1to 10 percent by weight, based on the total weight of the polycarbonateand aromatic sulfonate compound.

Halogenated materials may also be used as flame retardants, for examplehalogenated compounds and resins of formula (20):

wherein R is an alkylene, alkylidene or cycloaliphatic linkage, e.g.,methylene, ethylene, propylene, isopropylene, isopropylidene, butylene,isobutylene, amylene, cyclohexylene, cyclopentylidene, or the like; oran oxygen ether, carbonyl, amine, or a sulfur containing linkage, e.g.,sulfide, sulfoxide, sulfone, or the like. R can also consist of two ormore alkylene or alkylidene linkages connected by such groups asaromatic, amino, ether, carbonyl, sulfide, sulfoxide, sulfone, or thelike.

Ar and Ar′ in formula (20) are each independently mono- orpolycarbocyclic aromatic groups such as phenylene, biphenylene,terphenylene, naphthylene, or the like.

Y is an organic, inorganic, or organometallic radical, for example:halogen, e.g., chlorine, bromine, iodine, fluorine; ether groups of thegeneral formula OE, wherein E is a monovalent hydrocarbon radicalsimilar to X; monovalent hydrocarbon groups of the type represented byR; or other substituents, e.g., nitro, cyano, and the like, saidsubstituents being essentially inert provided that there is at least oneand preferably two halogen atoms per aryl nucleus.

When present, each X is independently a monovalent hydrocarbon group,for example an alkyl group such as methyl, ethyl, propyl, isopropyl,butyl, decyl, or the like; an aryl groups such as phenyl, naphthyl,biphenyl, xylyl, tolyl, or the like; and arylalkyl group such as benzyl,ethylphenyl, or the like; a cycloaliphatic group such as cyclopentyl,cyclohexyl, or the like. The monovalent hydrocarbon group may itselfcontain inert substituents.

Each d is independently 1 to a maximum equivalent to the number ofreplaceable hydrogens substituted on the aromatic rings comprising Ar orAr′. Each e is independently 0 to a maximum equivalent to the number ofreplaceable hydrogens on R. Each a, b, and c is independently a wholenumber, including 0. When b is not 0, neither a nor c may be 0.Otherwise either a or c, but not both, may be 0. Where b is 0, thearomatic groups are joined by a direct carbon-carbon bond.

The hydroxyl and Y substituents on the aromatic groups, Ar and Ar′, canbe varied in the ortho, meta or para positions on the aromatic rings andthe groups can be in any possible geometric relationship with respect toone another.

Included within the scope of the above formula are bisphenols of whichthe following are representative: 2,2-bis-(3,5-dichlorophenyl)-propane;bis-(2-chlorophenyl)-methane; bis(2,6-dibromophenyl)-methane;1,1-bis-(4-iodophenyl)-ethane; 1,2-bis-(2,6-dichlorophenyl)-ethane;1,1-bis-(2-chloro-4-iodophenyl)ethane;1,1-bis-(2-chloro-4-methylphenyl)-ethane;1,1-bis-(3,5-dichlorophenyl)-ethane;2,2-bis-(3-phenyl-4-bromophenyl)-ethane;2,6-bis-(4,6-dichloronaphthyl)-propane;2,2-bis-(2,6-dichlorophenyl)-pentane;2,2-bis-(3,5-dibromophenyl)-hexane; bis-(4-chlorophenyl)-phenyl-methane;bis-(3,5-dichlorophenyl)-cyclohexylmethane;bis-(3-nitro-4-bromophenyl)-methane;bis-(4-hydroxy-2,6-dichloro-3-methoxyphenyl)-methane; and2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane 2,2bis-(3-bromo-4-hydroxyphenyl)-propane. Also included within the abovestructural formula are: 1,3-dichlorobenzene, 1,4-dibromobenzene,1,3-dichloro-4-hydroxybenzene, and biphenyls such as2,2′-dichlorobiphenyl, polybrominated 1,4-diphenoxybenzene,2,4′-dibromobiphenyl, and 2,4′-dichlorobiphenyl as well as decabromodiphenyl oxide, and the like.

Also useful are oligomeric and polymeric halogenated aromatic compounds,such as a copolycarbonate of bisphenol A and tetrabromobisphenol A and acarbonate precursor, e.g., phosgene. Metal synergists, e.g., antimonyoxide, may also be used with the flame retardant. When present, halogencontaining flame retardants can be present in amounts of 0.1 to 10percent by weight, based on the total weight of the polycarbonate andaromatic sulfonate compound.

Inorganic flame retardants may also be used, for example salts of C₂₋₁₆alkyl sulfonate salts such as potassium perfluorobutane sulfonate (Rimarsalt), potassium perfluoroctane sulfonate, tetraethylammoniumperfluorohexane sulfonate, and potassium diphenylsulfone sulfonate, andthe like; salts formed by reacting for example an alkali metal oralkaline earth metal (for example lithium, sodium, potassium, magnesium,calcium and barium salts) and an inorganic acid complex salt, forexample, an oxo-anion, such as alkali metal and alkaline-earth metalsalts of carbonic acid, such as Na₂CO₃, K₂CO₃, MgCO₃, CaCO₃, and BaCO₃or fluoro-anion complexes such as Li₃AlF₆, BaSiF₆, KBF₄, K₃AlF₆, KAlF₄,K₂SiF₆, and/or Na₃AlF₆ or the like. When present, inorganic flameretardant salts can be present in amounts of 0.1 to 5 percent by weight,based on the total weight of the polycarbonate and aromatic sulfonatecompound.

Anti-drip agents may also be used, for example a fibril forming ornon-fibril forming fluoropolymer such as polytetrafluoroethylene (PTFE).The anti-drip agent may be encapsulated by a rigid copolymer asdescribed above, for example styrene-acrylonitrile copolymer (SAN). PTFEencapsulated in SAN is known as TSAN. Encapsulated fluoropolymers may bemade by polymerizing the encapsulating polymer in the presence of thefluoropolymer, for example an aqueous dispersion. TSAN may providesignificant advantages over PTFE, in that TSAN may be more readilydispersed in the composition. A suitable TSAN may comprise, for example,50 wt % PTFE and 50 wt % SAN, based on the total weight of theencapsulated fluoropolymer. The SAN may comprise, for example, 75 wt %styrene and 25 wt % acrylonitrile based on the total weight of thecopolymer. Alternatively, the fluoropolymer may be pre-blended in somemanner with a second polymer, such as for, example, an aromaticpolycarbonate resin or SAN to form an agglomerated material for use asan anti-drip agent. Either method may be used to produce an encapsulatedfluoropolymer. Antidrip agents can be used in amounts of 0.1 to 5percent by weight, based on the total weight of the polycarbonate andaromatic sulfonate compound.

While it is contemplated that other resins may be used in thethermoplastic compositions described herein, the aromatic sulfonatecompounds are particularly suited for use in thermoplastic compositionsthat contain only polycarbonate-type resins as described herein(homopolycarbonates, copolyester carbonates, and combinations thereof).Thus, in an embodiment, a thermoplastic composition consists essentiallyof a polycarbonate resin and 0.1 to 5 mmol/Kg of an aromatic sulfonatecompound, 0.2 to 4 mmol/Kg of an aromatic sulfonate compound, 0.3 to 3mmol/Kg of an aromatic sulfonate compound, or 0.4 to 2.5 mmol/Kg of anaromatic sulfonate compound, each weight being based on the combinedweight of the polycarbonate resin and the aromatic sulfonate compound,excluding any other additives and/or fillers. Alternatively, in anembodiment, a thermoplastic composition consists essentially of 99.75 to99.999 wt % of a polycarbonate and 0.001 to 0.25 wt % of an aromaticsulfonate compound, 99.8 to 99.998 wt % of a polycarbonate and 0.002 to0.2 wt % of a aromatic sulfonate compound, 99.85 to 99.997 wt % of apolycarbonate and 0.003 to 0.15 wt % of a aromatic sulfonate compound,99.9 to 99.996 wt % of a polycarbonate and 0.004 to 0.1 wt % of aaromatic sulfonate compound or 99.905 to 99.995 wt % of a polycarbonateand 0.005 to 0.095 wt % of an aromatic sulfonate compound, wherein eachof the foregoing weight percentages is based on the combined weight ofthe polycarbonate and the aromatic sulfonate compound, excluding anyother additives and/or fillers.

In another embodiment, the thermoplastic composition further comprises0.001 to 1 wt % of an aliphatic diol, based on the combined weight ofthe polycarbonate and the aromatic sulfonate compound. In anotherspecific embodiment, the thermoplastic composition comprises 0.001 to 1wt % of hydrolysis stabilizer, based on the combined weight of thepolycarbonate and the aromatic sulfonate compound.

In a further embodiment, the thermoplastic composition may comprise anadditive selected from impact modifier, filler, antioxidant, heatstabilizer, light stabilizer, ultraviolet light absorber, plasticizer,mold release agent, lubricant, antistatic agent, pigment, dye, flameretardant, anti-drip agent, or a combination comprising at least one ofthese.

The thermoplastic composition may be manufactured by methods generallyavailable in the art, for example, in one embodiment, in one manner ofproceeding, powdered polycarbonate, aromatic sulfonate compound, andother optional components including ionizing radiation stabilizingadditive and/or hydrolysis stabilizer are first blended, in aHENSCHEL-Mixer® high speed mixer. Other low shear processes includingbut not limited to hand mixing may also accomplish this blending. Theblend is then fed into the throat of an extruder via a hopper.Alternatively, one or more of the components may be incorporated intothe composition by feeding directly into the extruder at the throatand/or downstream through a sidestuffer. The powdered polycarbonate,aromatic sulfonate compound, and other optional components includingionizing radiation stabilizing additive and/or hydrolysis stabilizer mayalso be compounded into a masterbatch and fed into the extruder andcombined with additional polycarbonate and/or other polymers. Theextruder is generally operated at a temperature higher than thatnecessary to cause the composition to flow. The extrudate is immediatelyquenched in a water batch and pelletized. The pellets, so prepared, whencutting the extrudate may be one-fourth inch long or less as desired.Such pellets may be used for subsequent molding, shaping, or forming.

In a specific embodiment, a method of preparing a thermoplasticcomposition comprises melt combining a polycarbonate and an aromaticsulfonate compound. The melt combining can be done by extrusion. In anembodiment, the proportions of polycarbonate and aromatic sulfonatecompound are selected such that the optical properties of thethermoplastic composition are maximized while mechanical performance isat a desirable level. In a further specific embodiment, an ionizingradiation stabilizing additive is combined with the polycarbonate andaromatic sulfonate compound to make the thermoplastic composition. In afurther specific embodiment, a hydrolysis stabilizer is also included.In an embodiment, the thermoplastic composition is prepared bymelt-blending the masterbatch composition and a polycarbonate resin. Inan embodiment, the proportions of polycarbonate, aromatic sulfonatecompound, any added polycarbonate resin, and where desired, ionizingradiation stabilizing additive and/or hydrolysis stabilizer, areselected such that the optical properties of the thermoplasticcomposition are optimized while mechanical performance is at a desirablelevel.

In a specific embodiment, the extruder is a twin-screw extruder. Theextruder is typically operated at a temperature of 180 to 385° C.,specifically 200 to 330° C., more specifically 220 to 300° C., whereinthe die temperature may be different. The extruded thermoplasticcomposition is quenched in water and pelletized.

Shaped, formed, or molded articles comprising the thermoplasticcompositions are also provided. The thermoplastic compositions may bemolded into useful shaped articles by a variety of means such asinjection molding, extrusion, rotational molding, blow molding,thermoforming, or other methods such as melt casting or solvent casting.In a specific embodiment, molding is done by injection molding.Desirably, the thermoplastic composition has excellent mold fillingcapability and is useful to form articles such as, for example, bottles,syringes, dialysis fittings, tubing, sample vials, blood bags, petridishes, beakers, centrifuge tubes, spatulas, connectors, trocars,stopcocks, luer locks, Y-sites, catheters, oxygenator housings, trays,dental instruments, pipettes, glucose meters, inhalers, and the like.

The thermoplastic composition is further illustrated by the followingnon-limiting examples.

All thermoplastic compositions were compounded on a Werner & Pfleidererco-rotating twin screw extruder (Length/Diameter (L/D) ratio=30/1,vacuum port located near die face). The twin-screw extruder had enoughdistributive and dispersive mixing elements to produce good mixing ofthe polymer compositions. The compositions are subsequently moldedaccording to ISO 294 on a Husky or BOY injection molding machine.Compositions were compounded and molded at a temperature of 250 to 330°C., though it will be recognized by one skilled in the art that themethod is not limited to these temperatures.

The thermoplastic compositions are tested for the following properties.Yellowness Index (YI) for laboratory scale samples was determined usinga Gretag MacBeth Color System at an illuminant observer of C/2°, inaccordance with ASTM D1925-70 on 3.2±0.12 millimeter thick moldedplaques. The increase in YI (dYI) is calculated by subtracting theyellowness index value of a non-irradiated sample from that of anirradiated sample of the same composition. Molecular weight change wastested under conditions of either heat at 80° C. in a dry, nitrogenpurged oven, or heat and moisture at 80° C. and 80% relative humidity(80/80), according to the following procedure: a 100 gram sample of thepolycarbonate was placed in either an oven at 80° C. plus or minus 3°C., and a relative humidity of 80% was established by introduction ofwater vapor; alternatively, an oven was preheated to 80° C., and streamof dry air was purged through the chamber. The sample was maintained atthe desired temperature for 2 weeks (wk). The sample was removed fromthe oven, dissolved in methylene chloride, diluted to a concentration of1 mg/ml, and was analyzed by gel permeation chromatography using acrosslinked styrene-divinylbenzene column and calibrated againstpolycarbonate standards. The difference in weight averaged molecularweight is determined from a comparison of the weight averaged molecularweights of a sample and control.

Polycarbonate compositions for the examples (abbreviated Ex. in thefollowing tables) and comparative examples (abbreviated CEx. in thefollowing tables) were prepared using the components shown in Table 1.Each of the polycarbonate compositions were formulated to contain a moldrelease additive (0.27 wt % PETS), antioxidant (0.027 wt % Irgafos®1-168), and unless otherwise noted contain alkylene diol (0.15 wt %MPD). The polycarbonate resins and additives were blended in a powdermixer, extruded on a twin-screw extruder, and injection molded intoflat, rectangular plaques of 3.2±0.12 mm thickness, using the equipmentdescribed above. For testing of resistance to yellowing, the plaqueswere sealed and subjected to high-energy (gamma) irradiation, YI wasmeasured as soon as the plaques were exposed to the atmosphere, and dYIwas calculated according to the procedure above.

TABLE 1 BPA-PC BPA polycarbonate resin (MVR = 17.5 g/ GE Plastics 10 minat 300° C.) ITR-PC (19 mol % isophthalate-terephthalate- GE Plasticsresorcinol)-co-(75 mol % bisphenol-A polycarbonate-co-6 mol % resorcinolpolycarbonate) copolymer (Mw = 30,100 g/mol, PC standards) PTP4,4-Bis-(phenyl-p-toluenesulfonate)-2,2- See Procedure, propane belowPDT 1,4-Phenyl-ditosylate See Procedure, below 1,3,5-PTTPhloroglucinyl-tris-(tosylate) See Procedure, below 1,2,3-PTTPyrogallol-tris-(tosylate) See Procedure, below PTMBPyrogallol-tris(4-methoxy-benzene- See Procedure, sulfonate) below PTOSPyrogallol-tris(octanesulfonate) See Procedure, below PT Phenyltosylate, 98% purity TCI Americas Inc. MPD 2-Methyl-2,4-pentanediol(hexylene Aldrich glycol), 99% purity Chemical Co. PETS Pentaerythritoltetrastearate (plasticizer/ FACI Farasco, mold release agent) Genova,Italy I-168 IRGAFOS ® 168 Antioxidant (Tris Ciba Specialty(2,6-di-tert-butylphenyl)phosphite) Chemicals ERL-4221 CycloaliphaticEpoxide Resin ERL-4221 Union Carbide Corporation ADR-4368 JONCRYL ®ADR-4368 hydrolysis Johnson stabilizer Polymer

The aromatic sulfonate compounds4-bis-(phenyl-p-toluenesulfonate)-2,2-propane (PTP),1,4-phenyl-ditosylate (PDT), phloroglucinyl-tris-(tosylate)(1,3,5-PTT),pyrogallol-tris-(tosylate)(1,2,3-PTT),pyrogallol-tris(4-acetyl-benzenesulfonate) (PTAB),pyrogallol-tris(4-methoxy-benzenesulfonate) (PTMB), andpyrogallol-tris(octanesulfonate) (PTOS) were prepared according to theprocedures below.

4,4-Bis-(phenyl-p-toluenesulfonate)-2,2-propane (PTP). Into a 500 mlthree-necked round-bottom flask equipped with a magnetic stirrer, wascharged TsCl (10.0 g, 0.052 mol), BPA (5.38 g, 0.024 mol), andtetrahydrofuran (THF) (300 ml). Into this solution, TEA (5.61 g, 0.055mol) was added drop-wise via an addition funnel over a period of 5 min.After the addition of TEA, the solution was stirred for an additional 15min. The triethylamine hydrochloride was filtered and the THF wasremoved in vacuo. The crude product was diluted into 200 ml of CH₂Cl₂and subsequently transferred to a 500 ml separatory funnel. The solutionwas washed with 100 ml of 0.1 M NaOH (2×), 100 ml of 1.0 M HCl (2×), and100 ml of deionized water (2×). The methylene chloride layer wasextracted, dried over MgSO₄ for 1 hour, and filtered. The methylenechloride was removed in vacuo, and a viscous oil was recovered. Theviscous oil was diluted with a minimal amount of methylene chloride andcrystallized from hexanes to afford PTP as white crystals. The crystalswere collected and dried in vacuo (30 mm Hg) overnight.

1,4-Phenyl-ditosylate (PDT). Into a 500 ml three-necked round-bottomflask equipped with a magnetic stirrer, was charged TsCl (20.0 g, 0.105mol), hydroquinone (5.0 g, 0.045 mol), methylene chloride (400 ml), andTHF (50 ml). Into this solution, TEA (10.8 g, 0.106 mol) was addeddrop-wise via an addition funnel over a period of 10 min. After theaddition of TEA, the solution was stirred for an additional 2 hours andsubsequently transferred to a 1000 ml separatory funnel. The solutionwas washed with 150 ml of 1.0 M HCl (1×), 100 ml of 0.1 M NaOH (2×), 100ml of 1.0 M HCl (1×), and 100 ml of deionized water (2×). The methylenechloride layer was extracted, dried over MgSO₄ for 1 hour, and filtered.The methylene chloride was removed in vacuo, and a viscous oil wasrecovered. The viscous oil was diluted with a minimal amount ofmethylene chloride and crystallized from hexanes to afford PDT as whitecrystals. The crystals were collected and dried in vacuo (30 mm Hg)overnight.

Phloroglucinyl-tris-(tosylate)(1,3,5-PTT). Into a 500 ml three-neckedround-bottom flask equipped with a magnetic stirrer, was charged TsCl(20.0 g, 0.105 mol), phloroglucinol, (4.26 g, 0.033 mol), methylenechloride (400 ml), and THF (50 ml). Into this solution, TEA (13.2 g,0.13 mol) was added drop-wise via an addition funnel over a period of 10min. After the addition of TEA, the solution was stirred for anadditional 15 min and subsequently transferred to a 1000 ml separatoryfunnel. The solution was washed with 150 ml of 1.0 M HCl (1×), 100 ml of0.1 M NaOH (2×), 100 ml of 1.0 M HCl (1×), and 100 ml of deionized water(3×). The methylene chloride layer was extracted, dried over MgSO₄ for 1hour, and filtered. The methylene chloride was removed in vacuo, and aviscous oil was recovered. The viscous oil was diluted with a minimalamount of methylene chloride and crystallized from methanol to afford1,3,5-PTT as white crystals. The crystals were collected and dried invacuo (30 mm Hg) overnight.

Pyrogallol-tris-(tosylate)(1,2,3-PTT). Into a 500 ml three-neckedround-bottom flask equipped with a magnetic stirrer, was charged TsCl(10.0 g, 0.052 mol), pyrogallol (2.1 g, 0.017 mol), methylene chloride(300 ml), and THF (50 ml). Into this solution, TEA (5.26 g, 0.052 mol)was added drop-wise via a syringe over a period of 5 min. After theaddition of TEA, the solution was stirred for an additional 2 hours andsubsequently transferred to a 1000 ml separatory funnel. The solutionwas washed with 150 ml of 1.0 M HCl (1×), 100 ml of 0.1 M NaOH (2×), 100ml of 1.0 M HCl (1×), and 100 ml of deionized water (2×). The methylenechloride layer was extracted, dried over MgSO₄ for 1 hour, and filtered.The methylene chloride was removed in vacuo, and a viscous oil wasrecovered. The viscous oil was diluted with a minimal amount ofmethylene chloride and crystallized from hexanes to afford 1,2,3-PTT aswhite crystals. The crystals were collected and dried in vacuo (30 mmHg) overnight.

Pyrogallol-tris(4-acetyl-benzenesulfonate) (PTAB). Into a 500 mlthree-necked round-bottom flask equipped with a magnetic stirrer, wascharged 4-acetyl-benzenesulfonyl chloride (10.0 g, 0.045 mol),pyrogallol (1.9 g, 0.015 mol), methylene chloride (300 ml), and THF (50ml). Into this solution, TEA (4.7 g, 0.046 mol) was added drop-wise viaa syringe over a period of 5 min. After the addition of TEA, thesolution was stirred for an additional 2 hours and subsequentlytransferred to a 1000 ml separatory funnel. The solution was washed with150 ml of 1.0 M HCl (1×), 100 ml of 0.1 M NaOH (2×), 100 ml of 1.0 M HCl(1×), and 100 ml of deionized water (2×). The methylene chloride layerwas extracted, dried over MgSO₄ for 1 hour, and filtered. The methylenechloride was removed in vacuo, and a viscous oil was recovered. Theviscous oil was diluted with a minimal amount of methylene chloride andcrystallized from hexanes to afford PTAB as white crystals. The crystalswere collected and dried in vacuo (30 mm Hg) overnight.

Pyrogallol-tris(4-methoxy-benzenesulfonate) (PTMB). Into a 500 mlthree-necked round-bottom flask equipped with a magnetic stirrer, wascharged 4-methoxy-benzenesulfonyl chloride (10.0 g, 0.048 mol),pyrogallol (1.97 g, 0.016 mol), methylene chloride (300 ml), and THF (50ml). Into this solution, TEA (4.9 g, 0.048 mol) was added drop-wise viaa syringe over a period of 5 min. After the addition of TEA, thesolution was stirred for an additional 2 hours and subsequentlytransferred to a 1000 ml separatory funnel. The solution was washed with150 ml of 1.0 M HCl (1×), 100 ml of 0.1 M NaOH (2×), 100 ml of 1.0 M HCl(1×), and 100 ml of deionized water (2×). The methylene chloride layerwas extracted, dried over MgSO₄ for 1 hour, and filtered. The methylenechloride was removed in vacuo, and a viscous oil was recovered. Theviscous oil was diluted with a minimal amount of methylene chloride andcrystallized from hexanes to afford PTMB as white crystals. The crystalswere collected and dried in vacuo (30 mm Hg) overnight.

Pyrogallol-tris(octanesulfonate) (PTOS). Into a 500 ml three-neckedround-bottom flask equipped with a magnetic stirrer, was chargedoctanesulfonyl chloride (10.0 g, 0.047 mol), pyrogallol (1.9 g, 0.015mol), methylene chloride (300 ml), and THF (50 ml). Into this solution,TEA (5.0 g, 0.049 mol) was added drop-wise via a syringe over a periodof 5 min. After the addition of TEA, the solution was stirred for anadditional 2 hours and subsequently transferred to a 1000 ml separatoryfunnel. The solution was washed with 150 ml of 1.0 M HCl (1×), 100 ml of0.1 M NaOH (2×), 100 ml of 1.0 M HCl (1×), and 100 ml of deionized water(2×). The methylene chloride layer was dried over MgSO₄ for 1 hour andfiltered. The methylene chloride was removed in vacuo, and a viscous oilrecovered. The viscous oil was diluted with a minimal amount ofmethylene chloride and crystallized from hexanes to afford PTOS as whitecrystals. The crystals were collected and dried in vacuo (30 mm Hg)overnight.

Examples 1-7 and Comparative Examples 1-7. Sulfonates and 0.15 wt % MPDwere blended with BPA-PC polycarbonate resin according to the ratiosdescribed in Table 2, below. All examples and comparative examplescontain 0.27 wt % PETS (plasticizer/mold release agent) and 0.027 wt %Irgafos® I-168 (antioxidant). The pellets were injection molded on a BOYinjection molding machine into rectangular 3.2±0.12 mm thick plaquesthat were placed into a sealed package to prevent contact with light andmoisture. The plaques were then subjected to high energy irradiation atnominal doses of 25, 50, or 75 kiloGrays (kGy) (common forsterilization; actual doses are reported in the tables), andsubsequently measured for the change in yellowness index (dYI) accordingto the method described above which uses YI measurements according toASTM D1925-70. Table 3 shows the dYI data for the examples afterexposure to high energy gamma irradiation.

The compositions described in Table 2 were molded into plaques andevaluated for different mechanical, thermal, and physical properties. Acomparison of the resulting data is provided in Table 2. (Doses reportedwith the data are actual measured doses, and correspond to the nominaldoses as shown in the Table 2 notes).

TABLE 2* Sulfonate Loading dYI dYI Example Compound (mmol/Kg) (32 kGy¹)(59 kGy¹) Comp. Ex. 1 — 0 5.6 9.7 Comp. Ex. 2 PTs 1 6.6 9.7 Comp. Ex. 3PTs 2 8.3 11.1 Comp. Ex. 4 PTP 1 5.6 10.0 Comp. Ex. 5 PTP 2 5.2 9.5Comp. Ex. 6 PDT 1 5.5 10.2 Comp. Ex. 7 PDT 2 4.7 9.1 Ex. 1 1,3,5-PTT 14.9 9.1 Ex. 2 1,2,3-PTT 1 4.4 7.8 Ex. 3 1,2,3-PTT 2 4.3 7.4 Ex. 4 PTAB 20.7 4.7 Ex. 5 PTMB 2 3.1 7.4 Ex. 6 PTOS 1 4.9 8.1 Ex. 7 PTOS 2 −1.7 2.3*All examples and comparative examples contain 0.15 wt % MPD.¹Irradiation doses reported in kiloGrays (kGy) are actual doses. A 25kGy nominal dose gave a 32 kGy actual dose; and a 50 kGy nominal dosegave a 59 kGy actual dose. ²dYI values represent gain in YI compared tobefore-irradiation samples. A negative value indicates a loss in YI.

Examples 1-7 all show improved resistance to increase in dYI afterexposure to high energy dosages compared to Comparative Example 1, whichdoes not contain a sulfonate additive. The monofunctional (PT;Comparative Examples 2 and 3), and difunctional aromatic tosylates (PTPand PDT; Comparative Examples 4-7) did not show a significantimprovement in resistance to increase in dYI in comparison to thecontrol. For the tri-functional tosylates, the tosylates based onpyrogallol (1,2,3-PTT; Examples 2 and 3) show a greater resistance toincrease in dYI than the tri-tosylate of phloroglucinol (Example 1).Examples 6 and 7, prepared with 1,2,3-trifunctionalaromatic-alkylsulfonate (PTOS), appear to exhibit the greatestresistance to increase in dYI; however, the initial YI of thepolycarbonate composition containing PTOS was nearly twice the YI of anyof the polycarbonate compositions containing sulfonate additives,presumably due to thermal degradation of the alkyl moiety duringextrusion and injection molding (as found using thermogravimetricanalysis (TGA)). In most of the cases, doubling the sulfonateconcentration improved the dYI slightly, but not significantly. Thus,Examples 9 and 10 (PTOS) showed the most significant improvement in thedYI with a doubling the concentration of the PTOS from 1 mmol/Kg to 2mmol/Kg.

Examples 8-15 and Comparative Examples 8-11 were prepared according tothe ratios in Table 3 to examine the effect of the presence or absenceof aliphatic diol (MPD) in a polycarbonate composition comprising BPA-PCor ITR-PC and 1,2,3-PTT. The materials were blended, extruded on atwin-screw extruder, and injection-molded into flat, rectangular3.2±0.12 mm thick plaques, as described above. The dYI was determinedfor post gamma-irradiation of samples (nominal 25, 50, and 75 kGyirradiation doses; actual dose is noted in Table 3) using ASTM D1925-70.The data are given in Table 3.

TABLE 3 1,2,3-PTT dYI dYI dYI loading MPD (32 (51 (83 Resin (mmol/Kg)(wt %) kGy)^(1,2) kGy)^(1,2) kGy)^(1,2) CEx. 8 BPA-PC 0 0 16.7 31.0 43.6CEx. 9 BPA-PC 0 0.1 9.1 16.2 29.7 CEx. 10 BPA-PC 0 0.15 — — 47 Ex. 8BPA-PC 1 0 — — 21 Ex. 9 BPA-PC 1 0 10.4 16.6 23.1 Ex. 10 BPA-PC 2 0 — —19 Ex. 11 BPA-PC 1 0.15 — — 11 Ex. 12 BPA-PC 2 0.15 — — 11 CEx. 11 BPA-0 0.15 8 13.3 19.9 PC/ITR Ex. 13 BPA- 1 0 8.2 12.7 18.3 PC/ITR Ex. 14BPA- 2 0 6.8 10.3 14.1 PC/ITR Ex. 15 BPA- 2 0.15 2.5 4.4 6.6 PC/ITR¹Irradiation doses reported in kiloGrays (kGy) are actual doses. A 25kGy nominal dose gave a 32 kGy actual dose; a 50 kGy nominal dose gave a51 kGy actual dose; and a 75 kGy nominal dose gave an 83 kGy actualdose. ²dYI values represent gain in YI compared to before-irradiationsamples. A negative value indicates a loss in YI.

The data show that a polycarbonate resin that contains a combination ofMPD and a tri-functional tosylate (1,2,3-PTT) experiences a synergisticdecrease in the dYI (Examples 11, 12, and 15) when compared to a similarpolycarbonate material containing only the tri-functional tosylate(Examples 8-10, 13, and 14). Increasing the concentration of tosylatefrom 1 to 2 mmol/Kg did not significantly alter the dYI(post-irradiation). Of note, the ITR-PC examples (Examples 13-15, andComparative Example 11) have a lower baseline dYI at all exposure dosesthan the BPA-PC examples with corresponding additive loadings. Example15, prepared using ITR-PC with both MPD and 1,2,3-PTT added, shows thelowest dYI (and hence the highest stability) of the examples in Table 3.

Examples 16-22 and Comparative Examples 12 and 13. These examples wereprepared with BPA-PC, a multi-functional tosylate, 0.15 wt % MPD, and ahydrolysis stabilizer. Typically, the hydrolysis stabilizer is added toprevent or mitigate loss of molecular weight resulting from exposure ofthe polycarbonate compositions to an environment of elevated temperatureand elevated humidity. The hydrolysis stabilizers used were eitherERL-4221 or ADR-4368. The thermoplastic compositions were blended,extruded, molded into plaques for testing, and irradiated according tothe procedure described above. Identical plaques were placed into anoven for environmental exposure at either 80° C. or a combination of 80°C. and 80% humidity, as described above. The composition and data aregiven in Table 4.

TABLE 4 % Mw loss Hydr. (post-51 kGy % Mw loss Sulfonate Stab. dYI dYI 2wk, (post-51 kGy Load Hydr. Load (post 51 kGy; (post 83 kGy; 80° C./80%irradiation, 2 wk, Sulfonate (wt %) Stab. (wt %) gain)^(1,2) gain)^(1,2)RH)^(1,3) 80° C.)^(1,3) CEx. — 0 — 0 15.1 45.4 7 5.4 12 CEx. — 0 ADR0.25 14.7 36.4 8.2 5.4 13 4368 Ex. 16 1,3,5- 0.06^(‡) — 0 12.4 38 20.2 8PTT Ex. 17 1,3,5- 0.06^(‡) ADR 0.125 12.9 30.5 21.2 7.2 PTT 4368 Ex. 181,3,5- 0.06^(‡) ADR 0.25 12.7 31 18.7 5.8 PTT 4368 Ex. 19 1,3,5-0.06^(‡) ERL- 0.1 13.0 30.5 14.4 6.4 PTT 4221 Ex. 20 1,2,3- 0.06^(‡) — 06.8 12.4 30.4 15.9 PTT Ex. 21 1,2,3- 0.06^(‡) ADR 0.25 7.0 12.7 26.4 15PTT 4368 Ex. 22 1,2,3- 0.06^(‡) ERL- 0.1 6.6 12.1 28 11.8 PTT 4221^(‡)0.06 wt % of PTT (1,3,5- or 1,2,3-isomers) = 1.02 mmol/Kg¹Irradiation doses reported in kiloGrays (kGy) are actual doses. A 50kGy nominal dose gave a 51 kGy actual dose; and a 75 kGy nominal dosegave an 83 kGy actual dose. ²dYI values represent gain in YI compared tobefore-irradiation samples. A negative value indicates a loss in YI. ³%Mw loss represents loss in value compared to before-irradiation samples.A negative value indicates a loss in YI.

Examples 16-19 (with 1,3,5-PTT) show a marginal improvement over theComparative Examples 12 and 13 after irradiation by gamma rays, and afurther slight improvement in the dYI with an added epoxide stabilizer(Examples 17-19). Examples 20-22 (with 1,2,3-PTT) have a low dYIcompared to Comparative Examples 12 and 13, but the addition of epoxidestabilizer (Examples 21 and 22) did not appreciably affect the dYI. Inall cases, the epoxide additives did not significantly improve thehydrolytic stability of the polycarbonate resin. It is believed that theepoxide moieties may be reacting with other high-energy species that areformed during the gamma irradiation of polycarbonate, mitigating theirusefulness as hydrolysis stabilizers when exposed to heat and moisture,post-irradiation.

Generally, the data above show that low color or colorless articles(i.e., having low or no added colorant) having good optical propertiessuch as low yellowness and were desired, high transparency, may beprepared using the thermoplastic compositions described herein. Sucharticles can maintain these desired properties after irradiation at highdoses (up to 83 kGy) of gamma radiation.

Compounds are described herein using standard nomenclature. A dash (“—”)that is not between two letters or symbols is used to indicate a pointof attachment for a substituent. For example, —CHO is attached throughthe carbon of the carbonyl (C═O) group. The singular forms “a,” “an,”and “the” include plural referents unless the context clearly dictatesotherwise. The endpoints of all ranges reciting the same characteristicor component are independently combinable and inclusive of the recitedendpoint. All references are incorporated herein by reference. The terms“first,” “second,” and the like herein do not denote any order,quantity, or importance, but rather are used to distinguish one elementfrom another.

While typical embodiments have been set forth for the purpose ofillustration, the foregoing descriptions should not be deemed to be alimitation on the scope herein. Accordingly, various modifications,adaptations, and alternatives may occur to one skilled in the artwithout departing from the spirit and scope herein.

1. A thermoplastic composition comprising: a polycarbonate, and anaromatic sulfonate compound of formula(Y)_(m)—Ar—(Z—S(O)₂—X)_(n) wherein each X is independently a substitutedor unsubstituted C₁-C₂₀ alkyl, substituted or unsubstituted C₁-C₂₀arylalkyl, substituted or unsubstituted C₆-C₂₀ aryl, or substituted orunsubstituted C₇-C₄₀ alkylaryl, Z is —O—or substituted or unsubstituted—(—O—C₁₋₂₀—)_(w)—O—, wherein w is 1 to 20, Ar is a C₆-C₆₂ aromaticgroup; m is 0-3 and n is 3-6; and each Y is independently C₁-C₂₀ alkyl,substituted C₁-C₂₀ alkyl, C₆-C₂₀ aryl, C₁-C₈ alkyl-substituted C₆-C₂₀aryl, halogen, nitro, C₁-C₂₀ alkoxycarbonyl, C₁-C₂₀ alkoxy, or C₁-C₂₀acyl, and a ionizing radiation stabilizing additive, wherein a moldedarticle having a thickness of 3.2±0.12 millimeters and consisting of thepolycarbonate, aromatic sulfonate compound, and an effective amount ofeach of a mold-release agent and an antioxidant has, after exposure to atotal gamma radiation dose of 83 kGy and when measured according to ASTMD1925-70, an increase in yellowness index (dYI) of less than or equal to45, when compared to the unexposed molded article.
 2. The thermoplasticcomposition of claim 1, comprising 0.001 to 500 mmol/Kg of the aromaticsulfonate compound, based on the total weight of the polycarbonate andaromatic sulfonate compound.
 3. The thermoplastic composition of claim1, comprising 0.001 to 5 mmol/Kg of the aromatic sulfonate compound,with the proviso that the amount of aromatic sulfonate compound does notexceed 0.5 wt% of the total weight of the polycarbonate and aromaticsulfonate compound.
 4. The thermoplastic composition of claim 1, whereinAr is a C₆ aromatic group having a valency of m+n, and wherein m+n is 6.5. The thermoplastic composition of claim 4, wherein at least two of the—Z—S(O)₂—X groups are substituted ortho to each other on the C₆ aromaticgroup.
 6. The thermoplastic composition of claim 1, wherein the ionizingradiation stabilizing additive is an aliphatic alcohol, an aromaticalcohol, an aliphatic diol, an aliphatic polyol, an aliphatic ether, anester, a diketone, an alkene, a thiol, thioethers, a cyclic thioether, asulfone, a dihydroaromatic, a diether, a nitrogen compound, or acombination comprising at least one of the foregoing.
 7. Thethermoplastic composition of claim 6 wherein the aliphatic diol has thestructure:HO—(C(A′)(A″))_(c)—S—(C(B′)(B″))_(d)—OH wherein A′, A″, B′, and B″ areeach individually H or C₁-C₆ alkyl; and wherein S is C₁- C₂₀ alkyl,C₂-C₂₀ alkyleneoxy, C₃-C₆ cycloalkyl, or C₃-C₆ substituted cycloalkyl;and wherein c and d are each 0 or 1, with the proviso that, where c andd are each 0, S is selected such that both —OH groups are not connecteddirectly to a single common carbon atom.
 8. The thermoplasticcomposition of claim 6, wherein a molded article having a thickness of3.2±0.12 millimeters and consisting of polycarbonate, aromatic sulfonatecompound, aliphatic diol, and an effective amount of each of a moldrelease agent and an antioxidant has, after exposure to a total gammaradiation dose of 83 kGy and when measured according to ASTM D1925-70,an increase in yellowness index (dYI) of less than or equal to 29, whencompared to the unexposed molded article.
 9. The thermoplasticcomposition of claim 6, wherein a molded article having a thickness of3.2±0.12 millimeters and consisting of polycarbonate, aromatic sulfonatecompound, aliphatic diol, and an effective amount of each of amold-release agent and an antioxidant has, after exposure to a totalgamma radiation dose of 59 kGy and when measured according to ASTMD1925-70, an increase in yellowness index (dYI) of less than or equal to9, when compared to the unexposed molded article.
 10. The thermoplasticcomposition of claim 6, wherein a molded article having a thickness of3.2±0.12 millimeters and consisting of polycarbonate, aromatic sulfonatecompound, aliphatic diol, hydrolysis stabilizer, and an effective amountof each of a mold-release agent and an antioxidant has, after exposureto a total gamma radiation dose of 32 kGy and when measured according toASTM D1925-70, an increase in yellowness index (dYI) of less than orequal to 5, when compared to the unexposed molded article.
 11. Thethermoplastic composition of claim 6, further comprising a hydrolysisstabilizer, wherein a molded article having a thickness of 3.2±0.12millimeters and consisting of polycarbonate, aromatic sulfonatecompound, aliphatic diol, hydrolysis stabilizer, and an effective amountof each of a mold-release agent and an antioxidant has, after exposureto a total gamma radiation dose of 83 kGy and when measured according toASTM D1925-70, an increase in yellowness index (dYI) of less than orequal to 35, when compared to the unexposed molded article.
 12. Thethermoplastic composition of claim 11, wherein a molded article having athickness of 3.2±0.12 millimeters and consisting of polycarbonate,aromatic sulfonate compound, aliphatic diol, hydrolysis stabilizer, andan effective amount of each of a mold-release agent and an antioxidanthas, after exposure to a total gamma radiation dose of 51 kGy and whenmeasured according to ASTM D1925-70, an increase in yellowness index(dYI) of less than or equal to 13, when compared to the unexposed moldedarticle.
 13. The thermoplastic composition of claim 1, furthercomprising an impact modifier, filler, antioxidant, heat stabilizer,light stabilizer, ultraviolet light absorber, plasticizer, mold releaseagent, lubricant, antistatic agent, pigment, dye, flame retardant,anti-drip agent, or a combination comprising at least one of these. 14.The thermoplastic composition of claim 13 wherein the pigment is PigmentBlue 15:4, Pigment Blue 28, or a combination comprising at least one ofthe foregoing.
 15. The thermoplastic composition of claim 1 wherein thearomatic sulfonate compound is 1,3,5-tri-(4-toluenesulfonyl) benezene,1,2,3-tri-(4-toluenesulfonyl) benezene,1,2,3-tri-(4-acetylbenzenesulfonyl) benezene, 1,2,3-tri-(4-tmethoxybenzenesulfonyl) benezene, 1,2,3-tri-(n-octanesulfonyl)benezene, or a combination comprising at least one of the foregoing. 16.A thermoplastic composition comprising: a polycarbonate, and 0.001 to500 mmol/Kg of an aromatic sulfonate compound of formula(Y)_(m)—Ar—(Z—S(O)₂—X)_(n) wherein each X is independently a substitutedor unsubstituted C₁-C₂₀ alkyl, substituted or unsubstituted C₁-C₂₀arylalkyl, substituted or unsubstituted C₆-C₂₀ aryl, or substituted orunsubstituted C₇-C₄₀ alkylaryl, Z is —O—or substituted or unsubstituted—(—O—C₁₋₂₀—)_(w)—O—, wherein w is 1 to 20, Ar is a C₆-C₆₂ aromaticgroup; m is 0-3 and n is 3-6; and each Y is independently C₁-C₂₀ alkyl,substituted C₁-C₂₀ alkyl, C₆-C₂₀ aryl, C₁-C₈ alkyl- substituted C₆-C₂₀aryl, halogen, nitro, C₁-C₂₀ alkoxycarbonyl, C₁-C₂₀ alkoxy, or C₁-C₂₀acyl; and a ionizing radiation stabilizing additive, wherein the amountof aromatic sulfonate compound is based on the total weight of thepolycarbonate and the aromatic sulfonate compound.
 17. A method ofmaking a thermoplastic composition comprising melt-blending: apolycarbonate, and an aromatic sulfonate compound of formula(Y)_(m)—Ar—(Z—S(O)₂—X)_(n) wherein each X is independently a substitutedor unsubstituted C₁-C₂₀ alkyl, substituted or unsubstituted C₁-C₂₀arylalkyl, substituted or unsubstituted C₆-C₂₀ aryl, or substituted orunsubstituted C₇-C₄₀ alkylaryl, Z is —O—or substituted or unsubstituted—(—O—C₁₋₂₀—)_(w)—O—, wherein w is 1 to 20, Ar is a C₆-C₆₂ aromaticgroup; m is 0-3 and n is 3-6; and each Y is independently C₁-C₂₀ alkyl,substituted C₁-C₂₀ alkyl, C₆-C₂₀ aryl, C₁-C₈ alkyl- substituted C₆-C₂₀aryl, halogen, nitro, C₁-C₂₀ alkoxycarbonyl, C₁-C₂₀ alkoxy, or C₁-C₂₀acyl, and a ionizing radiation stabilizing additive, wherein a moldedarticle having a thickness of 3.2±0.12 millimeters and consisting of thepolycarbonate, the aromatic sulfonate compound, and an effective amountof each of a mold-release agent and an antioxidant has, after exposureto a total gamma radiation dose of 83 kGy and when measured according toASTM D1925-70, an increase in yellowness index (dYI) of less than orequal to 45, when compared to the unexposed molded article.
 18. Amasterbatch composition comprising: a polycarbonate, and 5 to 500mmol/Kg of an aromatic sulfonate compound of formula(Y)_(m)—Ar—(Z—S(O)₂—X)_(n) wherein each X is independently a substitutedor unsubstituted C₁-C₂₀ alkyl, substituted or unsubstituted C₁-C₂₀arylalkyl, substituted or unsubstituted C₆-C₂₀ aryl, or substituted orunsubstituted C₇-C₄₀ alkylaryl, Z is —O—or substituted or unsubstituted—(—O—C₁₋₂₀—)_(w)—O—, wherein w is 1 to 20, Ar is a C₆-C₆₂ aromaticgroup; m is 0-3 and n is 3-6; and each Y is independently C₁-C₂₀ alkyl,substituted C₁-C₂₀ alkyl, C₆-C₂₀ aryl, C₁-C₈ alkyl- substituted C₆-C₂₀aryl, halogen, nitro, C₁-C₂₀ alkoxycarbonyl, C₁-C₂₀ alkoxy, or C₁-C₂₀acyl, and a ionizing radiation stabilizing additive, wherein the amountof aromatic sulfonate compound is based on the total weight of thepolycarbonate and the aromatic sulfonate compound, and wherein athermoplastic composition comprises the masterbatch composition and apolycarbonate resin.
 19. A method of making a thermoplastic compositioncomprising melt-blending: a masterbatch composition comprising: apolycarbonate, and an aromatic sulfonate compound of formula(Y)_(m)—Ar—(Z—S(O)₂—X)_(n) wherein each X is independently a substitutedor unsubstituted C₁-C₂₀ alkyl, substituted or unsubstituted C₁-C₂₀arylalkyl, substituted or unsubstituted C₆-C₂₀ aryl, or substituted orunsubstituted C₇-C₄₀ alkylaryl, Z is —O—or substituted or unsubstituted—(—O—C₁₋₂₀—)_(w)—O—, wherein w is 1 to 20, Ar is a C₆-C₆₂ aromaticgroup; m is 0-3 and n is 3-6; and each Y is independently C₁-C₂₀ alkyl,substituted C₁-C₂₀ alkyl, C₆-C₂₀ aryl, C₁-C₈ alkyl- substituted C₆-C₂₀aryl, halogen, nitro, C₁-C₂₀ alkoxycarbonyl, C₁-C₂₀ alkoxy, or C₁-C₂₀acyl; a polycarbonate resin; and a ionizing radiation stabilizingadditive, wherein a molded article having a thickness of 3.2±0.12millimeters and consisting of the polycarbonate, the aromatic sulfonatecompound, the polycarbonate resin, and an effective amount of each of amold-release agent and an antioxidant has, after exposure to a totalgamma radiation dose of 83 kGy and when measured according to ASTMD1925-70, an increase in yellowness index (dYI) of less than or equal to45, when compared to the unexposed molded article.
 20. An articlecomprising the thermoplastic composition of claim
 1. 21. The article ofclaim 20, wherein the article has a thickness of 3.2±0.12 millimetersand a transmission of greater than 95% according to ASTM D1003-00, andwherein these properties are maintained after gamma irradiation at atotal dose of up to 83 kGy.
 22. The thermoplastic composition of claim1, wherein each Y is independently fluoro, chloro, bromo, iodo, methoxycarbonyl, ethyl carbonyl, t-butyl carbonyl, cyclohexyl carbonyl, phenylcarbonyl, —OCH₃, —OCH₂CH₃, —O-t-butyl, —O-n-butyl, —O-n-octyl, acetyl,pivaloyl, n-octyloyl, n-dodecoyl, n-stearoyl, benzoyl, methyl, ethyl,propyl, isopropyl, butyl, sec-butyl, tert-butyl, n-pentyl, 2-pentyl,3-pentyl, isopentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl,dodecyl, octadecyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl,cyclohexyl, adamantyl, norbornyl, phenyl, C₁-C₈ alkylphenyl, C₁-C₈alkoxyphenyl, or halophenyl.
 23. The thermoplastic composition of claim1, wherein each Z is independently oxygen diradical, ethanedioxy,1,2-propanedioxy, 1,3-propanedioxy, 1,2- butanedioxy, 1,3-butanedioxy,1,4-butanedioxy, 2,3-butanedioxy, 1,2-pentanedioxy, 1,3- pentanedioxy,1,4-pentanedioxy, 1,5-pentanedioxy, 2,3-pentanedioxy, 2,4-pentanedioxy,2- methy1-1,2-butanedioxy, 2-methyl-1,3-butanedioxy,2-methyl-1,4-butanedioxy, 2-methy1-2,3- butanedioxy, 2,2-dimethyl-1,2-propanedioxy, 2,2-dimethyl-1,3-propanedioxy,3,3-dimethy1-1,2-propanedioxy, 1,1-dimethyl-2,3-propanedioxy,1,2-hexanedioxy, 1,3-hexanedioxy, 1,4- hexanedioxy, 1,5-hexanedioxy,1,6-hexanedioxy, 2,3-hexanedioxy, 2,4-hexanedioxy, 2,5- hexanedioxy,2-methyl-1,2-pentanedioxy, 2-methyl-1,3-pentanedioxy, 2-methyl-1,4-pentanedioxy, 2-methyl-2,3-pentanedioxy, 2-methyl-2,4-pentanedioxy,2,2-dimethy1-1,2- butanedioxy, 2,2-dimethyl- 1,3-butanedioxy,3,3-dimethyl- 1,2-butanedioxy, 1,1-dimethy1-2,3- butanedioxy,octanedioxy, decanedioxy, undecanedioxy, dodecanedioxy, hexadecanedioxy,octadecanedioxy, icosananedioxy, docosananedioxy, cyclopropanedioxy,cyclobutanedioxy, cyclopentanedioxy, cyclohexanedioxy, 1,4-dioxymethylcyclohexane, ethylenedioxy, 1,2- propylenedioxy, 1,3-propylenedioxy,1,2-butylenedioxy, 1,4-butylenedioxy, or 1,6-hexylenedioxy.
 24. Thethermoplastic composition of claim 1, wherein each X is independentlymethyl, ethyl, n-propyl, 2-methylpropyl, n-butyl, 2-methylbutyl,3-methylbutyl, n-pentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl,n-hexyl, cyclohexyl, n-octyl, 2- ethylhexyl, n-dodecyl, n-octadecyln-eicosyl, camphoryl, trifluoromethyl, 2,2,2-trifluoroethyl,perfluoroethyl, perfluoro-n-butyl, perfluoro-n-hexyl, perfluoro-n-octyl,perfluorocyclohexyl, perfluoro-(4-ethylcyclohexyl)-2-ethyl, benzyl,2-methylbenzyl, 3-methylbenzyl, 4-methylbenzyl, phenyl, 2-methylphenyl,3-methylphenyl, 4-methylphenyl, 3,5-dimethylphenyl, 2,3- dimethylphenyl,2,4-dimethylphenyl, 2,5-dimethylphenyl, 2,6-dimethylphenyl, 2,3,4-trimethylphenyl, 2,3,5-trimethylphenyl, 3,4,5-trimethylphenyl,2,4,6-trimethylphenyl, 4- ethylphenyl, 4-n-butylphenyl,4-tert-butylphenyl, 2-trifluoromethylphenyl, 4-trifluoromethylphenyl,4-methoxyphenyl, 4-tert-butoxyphenyl, 4-fluorophenyl, 4-chlorophenyl,4-bromophenyl, naphthyl, C₁-C₈ alkyl-substituted naphthyl, C₁-C₈ alkylether-substituted naphthyl, or halogen-substituted naphthyl.